STEAM  BOILERS 
ENGINES  &  TURBINES 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


STEAM    BOILERS,    ENGINES,    AND 
TURBINES 


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II 


STEAM  BOILERS,  ENGINES 
AND  TURBINES 


BY 

SYDNEY   F.   WALKER 

M.I.E.E.,    M.lNST.M.E.,    M.I.M.E.,    Assoc.M.I.C.E.,    ETC. 
AUTHOR  OF  "ELECTRICITY  IN  MINING,"  ETC. 


NEW   YORK 
D.    VAN    NOSTRAND    COMPANY 

23    MURRAY    AND    27    WARREN   STREETS 
1908 


PREFACE 

IN  the  following  pages  the  author  has  endeavoured  to  set  forth  the 
principles  and  practice  of  steam,  as  they  are  understood  by  modern 
engineers,  for  the  use  of  the  student,  using  the  term  in  its  wide 
sense,  viz.  to  include  all  those  to  whom  a  knowledge  of  steam  and  of 
steam-using  apparatus  will  be  of  service.  With  the  universal  em- 
ployment of  power,  a  knowledge  of  the  properties  of  steam  is  becoming 
daily  of  more  and  more  importance  to  engineers  of  all  branches,  and 
to  large  numbers  of  business  men  and  others  who  are  not  directly 
engaged  in  the  practical  application  of  steam  appliances. 

The  author  has  endeavoured  to  set  out,  in  simple  language,  and 
with  the  aid  of  only  the  very  simplest  forms  of  mathematics,  the 
properties  of  water,  of  steam,  of  air,  and  of  the  gases  that  enter  into 
the  process  of  combustion,  and  he  has  also  endeavoured  to  give  a 
resume  of  the  latest  practice  in  steam,  and  a  description  of  the  latest 
appliances  for  its  economical  generation  and  use.  With  the  ever- 
increasing  demands  for  power,  and  with  the  repeated  warnings  from 
scientists  of  the  possible  shortness  of  coal,  and  again  with  the 
steadily  increasing  cost  of  mining  coal  in  the  United  Kingdom, 
sources  of  economy  in  the  use  of  steam,  it  has  appeared  to  the 
author,  are  of  increasing  importance;  and  he  has  endeavoured  to 
give  a  clear  and  simple  explanation  of  the  different  apparatus 
designed  to  produce  economy,  and  of  the  leading  forms  on  the 
market. 

The  book  is  divided  into  six  chapters.  In  the  first  chapter  the 
author  has  dealt  with  the  underlying  principles  upon  which  the  use 
of  steam  apparatus  is  based.  In  the  second  chapter  he  has  described 
the  principles  and  construction,  and,  as  far  as  space  has  allowed,  the 
working  of  the  different  forms  of  boilers  on  the  market.  In  the 
third  chapter  he  has  dealt  with  the  apparatus  designed  to  effect 
economies  in  the  consumption  of  fuel.  In  the  remaining  chapters 

V 

181025 


vi"  PREFACE 

he  has  dealt  with  the  construction,  arrangement,  and  working  of 
reciprocating  engines,  turbines,  and  condensers,  and  with  the  appa- 
ratus designed  for  economies  in  steam  consumption,  in  the  cost 
of  condensing,  etc.  He  trusts  that  the  book  may  be  of  service 
to  those  for  whom  it  is  written,  and  may  be  an  aid  to  the  heavier 
books  on  steam,  steam  engines,  etc. 

SYDNEY  F.   WALKER, 

1,  BLOOMFIELD  CRESCENT, 
BATH. 


CONTENTS 

CHAPTEE    I 
INTRODUCTORY 

PAGE 

What  heat  is .         1 

The  ether       ....  1 

Properties  of  heat  waves  ..........         2 

Temperature  ......  4 

Absolute  temperature      ...........         5 

Measurement  of  temperatures          .....  5 

The  expansion  pyrometer        .  .         6 

Thermo-electric  pyrometers    .......  7 

Entropy          .........  .9 

Transmission  of  heat       ...........         9 

Thermal  conductivity  of  finely  divided  substances    ......       12 

Specific  heat 13 

The  British  thermal  unit      ......  .13 

The  mechanical  equivalent  of  heat  .........       15 

The  rate  of  doing  work 15 

Expansion  of  bodies  in  the  presence  of  heat .16 

Latent  heat .16 

The  variation  of  the  boiling-point 18 

The  influence  of  dissolved  substances  upon  the  boiling-point  of  water        .          .       21 
Absolute  pressure  ............       22 

Variation  of  the  latent  heat  with  variation  of  pressure      .....       22 

Properties  of  saturated  steam  .........       24 

Air 25 

Volume  and  weight  of  air  at  various  temperatures    ......       26 

Measuring  the  percentage  of  vapour  in  air  .          .         .  .          .28 

Volume  and  pressure      ...........       29 

The  specific  heat  of  air  .          .          .          .          .          .          .          .          .          .          .29 

Water ...       31 

Impurities  in  water         ...........       33 

Steam 34 

Superheated  steam          .....         \          .....       35 

Specific  heat  of  superheated  steam  ...  36 

Carnot's  law  of  the  efficiency  of  heat  engines  .......       36 

Fuel  and  combustion      ........  37 

Calorific  power 


Forms  of  fuel 
Coal      . 
Forms  of  coal 
Cannel  coal  . 


39 
39 
40 
41 


The  differences  between  coals          .........       42 

Carbon  and  volatile  matter  in  coals .42 

Calorimetry  .............       43 

vii  Cl    3 


viii  CONTENTS 

PAGE 

Wood 44 

Spent  tan,  straw,  bagasse,  corn  stalks,  and  other  organic  refuse        ...  45 

Liquid  fuels  .............  46 

Flash  point  and  ignition  point 47 

Gas  tar  as  a  fuel    ............  48 

Burning  liquid  fuels 49 

Gaseous  fuel           ............  49 

Producer  gas          ............  49 

Blast  furnace  gas  ............  50 

Coke  oven  gas         ............  51 

Natural  gas    .............  51 

Gases  found  in  collieries          ..........  52 

CHAPTEE    II 

BOILERS 

The  steam  boiler 53 

Circulation  in  boilers  ...........  54 

Fire-tube  boilers 55 

Galloway  cone  tubes  ...........  59 

The  construction  of  Lanes,  and  Cornish  boilers 60 

Lanes,  and  Cornish  boiler  flues        .........  63 

Corrugated  flues  and  furnaces          .........  64 

Setting  Cornish  and  Lanes,  boilers           ........  68 

Firing  Lanes,  and  Cornish  boilers  from  outside  ......  69 

The  Galloway  boiler 70 

Multitubular  boilers  ...........  70 

Forms  of  multitubular  boiler 72 

The  ordinary  multitubular  boiler    .........  72 

The  locomotive  type  of  boiler  .          .          .         .  .         .          .          .73 

The  marine  boiler  .         .         .         .         .         .         .         .          .         .         .         .73 

The  dry  back  boiler  ...........  74 

Combined  Cornish  and  multitubular  boilers 76 

Water-tube  boilers           ...........  77 

An  advantage  claimed  for  water-tube  boilers  with  high  pressures       ...  79 
Convenience  of  transport  of  water-tube  boilers          .         .          ...          .          .81 

The  water  circulation  in  water-tube  boilers      .......  81 

The  furnace  of  water-tube  boilers    .........  82 

Forms  of  water-tube  boilers  ..........  82 

The  Stirling  water-tube  boiler 84 

The  Nesdrum  water-tube  boiler  .........  87 

The  Woodeson  water-tube  boiler  .  . 88 

Water-tube  boilers  with  horizontal  or  nearly  horizontal  tubes  .          .          .  '      .  90 

Marshall's  water-tube  boiler  ..........  91 

Davey,  Paxman's  water-tube  boiler  ........  91 

The  Wood  water-tube  boiler 92 

The  Galloway  water-tube  boiler       .........  93 

American  boilers  with  straight,  or  nearly  straight,  horizontal  tubes  ...  93 

The  Atlas  water-tube  boiler 93 

The  water  purifying  apparatus  of  the  Atlas  boiler     ......  95 

The  Heine  and  the  Detroit  water-tube  boilers  .......  95 

Water-tube  boilers  with  vertical  tubes     ........  96 

Water-tube  boilers  with  curved  tubes  ........  98 

The  Climax  water-tube  boiler 98 

Thornycroft  water-tube  boilers  .........  99 

Thornycroft-Schultz  boiler 100 

The  Taylor  water-tube  boiler  .  . 104 

Small  vertical  boilers 104 

The  Straker  motor-wagon  boiler 105 


CONTENTS  ix 

CHAPTEE  III 

BOILER  ACCESSORIES 

PAGE 

Burning  the  fuel 107 

Special  forms  of  furnace  bars 108 

Apparatus  for  burning  coal  dust 110 

Apparatus  for  burning  liquid  fuel.— The  Holden  System Ill 

Liquid  fuel  burners.— Marshall's  Apparatus     .                                      ...  112 

Burning  town's  refuse    .....                                                .          .  113 

Meldrum's  colliery  refuse  destructor        .                                                                   .  114 

Mechanical  stokers          ...                                                                             .  115 

Forms  of  mechanical  stoker  .         .                                                                             .  117 

The  grate  bars  of  over-feed  stokers  .                                                                             .  120 
The  Auto  stoker     ....                                                                             .122 

Vicars  mechanical  stoker        .         .                                                                          .  123 

Chain-grate  stokers        ...                                                                             .  124 

Under-feed  stokers         ....  .125 

Providing  the  air  for  the  furnace    ...                            .                  .  127 

Chimney  draught 127 

Sizes  of  chimneys  and  horse-power  of  boilers  .                                      .                   .  131 

The  factors  ruling  the  height  of  a  chimney     .                                                          .  133 

Construction  of  boiler  chimneys     ....                                                .  137 

Forced  draught .  139 

Induced  draught 141 

Induced  draught  combined  with  heating  of  the  air  for  the  furnace    .                  .  143 

Forms  of  fans  employed  for  mechanical  draught      ....                   .  145 

Sizes  of  fan  required      .                   .                   .  146 

Draught  by  means  of  steam  jets     .........  147 

Boiler  dampers      ....                   .                             .                   .          .  148 

Automatic  damper  regulators                    .                   .                                                .  149 

The  Lagonda  damper  regulator       .                                                .                             .  149 

Boiler  cleaners       ....                                                ....  150 

Turbine  boiler-tube  cleaners            .                            ....  151 

Boiler  fittings        .  .151 

Safety  valves          ...                                                                             .  152 

Atmospheric  relief  valve 155 

High  and  low  water  safety  apparatus 155 

Combined  stop  and  safety  valve 156 

Heating  the  feed  water  for  the  boilers     .                                                                 .  156 

Economizers           .....                                                                   .  158 

Green's  Economizer .  160 

Heating  air  and  water  by  economizers     ...                                      .  162 

Steam  feed- water  heaters        ...                                                          .  163 

The  enclosed  steam  feed- water  heaters    ........  163 

Open  steam  feed-water  heaters        ...                   168 

Feed-water  pumps          ...                                                          .          .  170 

Earn  pumps            .                                                                                                          .  170 

Special  pumps       ...                                                                                       .  170 

The  Pulsometer  feed  pump     .                             .......  171 

Electrically  driven  boiler  feed  pumps      .                   ...                   .          .  172 

Donkey  or  wall  pumps  ...........  173 

Injectors 173 

Feed-water  regulators    .                                       .          .                                      .  178 

Purifying  the  feed  water         ...                                      ....  179 

Other  scale-forming  substances       .........  181 

Methods  of  removing  foreign  bodies,  etc 181 


x  CONTENTS 

PAGE 

Water  softeners 182 

The  Archbutt-Deeley  water  softener        .          .          .          .          .          .                   .  183 

The  Criton  water  softener 184 

The  Reisert  water  softener 186 

The  Bruun  Lowener  water  softener 187 

Guttman  water  softener         ..........  188 

Doulton's  water  softener 188 

The  Kennicott  water  softener          .          .          .          .          .         .          .          .          .189 

The  Desrumeaux  water  softener     .........  190 

The  Arthur  Koppel  water  softener           ........  191 

Harris-Anderson  water  softener      .........  192 

Removing  the  oil  from  the  water 193 

Oil  separators         ............  193 

Cochrane  vacuum  oil  separator ...  195 

Reid  oil  separators         ...........  195 

A  steam  exhaust  head  and  oil  catcher     ........  197 

Special  apparatus  for  removing  oil           ........  197 

Davis-Perrett's  electrical  emulsifier 198 

Superheating  the  steam          ..........  199 

Forms  of  superheating  apparatus    .........  200 

The  Babcock  Wilcox 200 

The  Stirling  superheater 201 

The  Nesdrum  Superheater 202 

The  Sinclair  Superheater 203 

The  Galloway  Superheater 203 

The  Tinker  Superheater 203 

Steam  separators            ...........  203 

The  Harriot  Steam  Separator 203 

Evaporators           ............  204 

Apparatus  for  testing  the  flue  gases  in  the  chimney          .....  205 

The  Sarco  automatic  C02  recorder 208 

The  Simmance  and  Abady  C02  recorder  ........  211 

The  Orsat  apparatus  for  flue  gas  analysis 212 


CHAPTER   IV 
THE  STEAM  ENGINE 

The  reciprocating  steam  engine 213 

The  mean  effective  pressure   ..........  215 

The  work  a  steam  engine  will  perform 218 

Indicated  horse-power  and  brake  horse-power  ......  219 

Double-cylinder  engines          ..........  220 

Compound  Engines .  .  221 

Triple-expansion  engines        ..........  226 

Quadruple-expansion  engines .  227 

High-  and  low-speed  engines  ..........  227 

The  Ernest  Scott  and  Mountain  high-speed  engine  .....  232 

The  Willans  central  valve  engine 232 

Bunsted  high-speed  engine .  236 

The  Peache  engine         ...........  237 

Vertical  and  horizontal  engines      .........  239 

Lancashire  mill  engines          ..........  240 

Reciprocating  valves  for  engines     .........  242 

The  slide  valve 243 

Giving  motion  to  the  slide  valve     .         .  .         .         .         .         .         .  246 

Objections  to  the  slide  valve 247 

Lap  and  lead  of  slide  valve     ..........  248 


CONTENTS  xi 

PAGE 

The  piston  slide  valve    .... 

Drop  valves  .............  249 

The  piston  drop  valve     ...                                                                   .  250 

Cornish  valves        ............  250 

The  Corliss  valve 251 

The  Hill  or  Wheelock  valve 253 

Stop  valves 254 

The  parallel  slide  stop  valve   ..........  256 

Centre  pressure  stop  valve ...  257 

Taking  the  power  from  the  piston  .          .          .          .          .          ...          .          .  260 

The  government  of  engines     ..........  265 

The  indicator 270 

Steam  pipes  .............  273 

Water  hammer      ............  275 

The  arrangement  of  steam  pipes      .........  278 

Steam  traps ...  280 

Brooke's  steam  trap      ..........  281 

Sirius  steam  trap           ..........  282 

The  Lancaster  steam  trap     .........  283 

The  water-seal  steam  trap 284 

Steam  traps  operating  by  the  expansion  of  a  volatile  spirit         ....  285 

The'Eeservoir  steam  trap 286 

The  Euston  steam  trap 286 

The  Anderson  trap 286 

Belief  valves                                                                     ...  287 


CHAPTEE  V 

THE  STEAM  TURBINE 

Classes  of  steam  turbines 288 

Difference  between  pressure  and  impulse  turbines    ......  291 

Compounding  in  pressure  turbines 292 

Forms  of  pressure  turbine       ..........  292 

The  Parsons  Turbine 292 

Bearings  of  Parsons  turbines          ....  ...  295 

Governor  of  Parsons  turbines         ........  296 

The  Willans  turbine  governor          .........  300 

Lubrication  of  the  Willans-Parsons  turbine 300 

The  Brush-Parsons  turbine 300 

The  De  Laval  turbine 301 

Government  of  the  De  Laval  turbine      ........  303 

Transmitting  the  power  of  the  De  Laval  turbine  wheel 305 

The  Curtis  turbine 309 

Governing  the  Curtis  turbine  .........  311 

Test  of  a  1500  Kilowatt  Curtis  turbo  generator 313 

Westinghouse  turbine     ...........  313 

The  Rateau  turbine 315 

The  A.E.G.  steam  turbine 316 

The  Zoelly  turbine 317 

The  Hamilton  Holzwarth  steam  turbine 321 

The  forms  of  buckets  and  blades  of  steam  turbines  ......  322 

Turbines  working  with  exhaust  steam 322 

Turbines  and  condensing         ..........  327 

Turbines  and  superheated  steam 328 


Xll 


CONTENTS 


CHAPTEE   VI 
CONDENSING  PLANT 

The  condenser        .... 

Forms  of  condenser 

The  surface  condenser    . 

The  evaporative  surface  condenser  . 

Eraser's  evaporative  condenser 

The  Wheeler  surface  condenser 

Open  tank  surface  condensers 

The  Contraflo  condenser 

Jet  condensers        .... 

The  Mirr lees- Watson  jet  condenser 

The  Worthington  jet  condenser 

The  Ejector  condenser  . 

The  Barometric  condenser 

Parsons  vacuum  augmenter    . 

Central  condensing  stations  . 

The  quantity  of  cooling  water  required  for  condensing 

Mr.  Richard  Allen's  experiments  on  condensers 

Prof.  Weighton's  experiments  on  condensers  . 

Pumps  for  condensers    ...... 

Air  pumps      ........ 

Bucket  air  pumps  ...... 

Cooling  the  circulating  water  for  condensers    . 
Cooling  ponds         ....... 

Cooling  ponds  with  nozzles     ..... 

Cooling  towers        ....... 

Cooling  towers  without  vertical  draught  . 
Chimney  cooling  towers  ..... 

The  cooling  tower  with  fan  draught 

Apparatus  used  in  cooling  towers    .... 

A  convex  splash  bar  cooling  tower  .... 

Construction  of  cooling  towers        .... 

INDEX  . 


PAGE 
330 
331 
331 
334 
335 
336 
338 
338 
340 
341 
341 
343 
344 
347 
348 
349 
352 
360 
363 
365 
366 
367 
368 
369 
370 
371 
372 
375 
376 
378 
379 

381 


LIST   OF    ILLUSTRATIONS 


FIG.  PAGE 

1.  Diagram  of  connections  of  Crornpton's  thermo-electric  pyrometer      .          .  8 

2.  Crornpton's  thermo-electric  pyrometer  arranged  for  pipe  ....  8 

3.  Arrangement  of  Crornpton's  thermo-electric  pyrometer  for  flue  .         .  8 

4.  Bristol's  thermo-electric  pyrometer  .          .         .         .          .         .          .  9 

5.  Sectional  drawing  of  internally  fired  "  Cornish  "  and  multitubular  boiler, 

made  by  Messrs.  Marshall     .........  56 

6.  Sectional  drawing  of  Lanes,  boiler  with  cone  tubes  .....  57 

7.  Section  of  Adamson  original  flange  seam  for  Lanes,  boiler  flues          .          .  63 

8.  Section  of  Adamson  absorber  flange  seam  for  Lanes,  boiler  flues         .          .  63 

9.  Sectional  elevation  and  plan  of  Lanes,  boiler  with  Adamson's  flues    .          .  64 

10.  Longitudinal  and  transverse   sections   of  Messrs.  Davey  and  Paxman's 

"  Economic  "  boiler      ..........  75 

11.  Sectional  view  of  Robb-Mumford  standard  boiler       .....  77 

12.  Longitudinal  and  transverse  section  of  the  "  Stirling  "  boiler,  with  super- 

heater ......                 ......  85 

13.  Sectional  drawings  of   "  Woodeson  "  water-tube  boiler,  made  by  Messrs. 

Clarke,  Chapman  &  Co 89 

14.  "  Wood  "  water-tube  boiler,  made  by  Messrs.  Fraser  and  Chalmers    .          .  92 

15.  Sectional  drawings  of  "  Suckling  "  water-tube  boiler          ....  97 

16.  Internal  view  of  Climax  water-tube  boiler,  showing  the  tubes,  vertical 

steam  drum,  etc. .          .          .98 

17.  Sections  of  Thorneycroft  water-tube  boiler,  "  Speedy  "  type       .          .          .  101 

18.  Sections  of  Thorneycroft  water-tube  boiler,  "  Daring  "  type        .          .          .  102 

19.  Sections  of  "  Hay "  water-tube  boiler 103 

20.  Sectional  elevation  of  Straker  boiler  for  steam  driven  vehicles  .         .          .  105 

21.  Furnace  grate  with  Neil's  rocking  fire  bars       ......  109 

22.  Neil's  furnace  front,  with  baffle  plate  between  the  furnace  and  fire  door     .  109 

23.  Arrangement  for  burning  coal  dust  in  a  Lanes,  boiler,  by  the  Schwartz- 

kopff  process        ...........  110 

24.  Sectional  drawings  of  Holden's  apparatus  for  burning  liquid  fuel        .          .  Ill 

25.  Marshall's  apparatus  for  burning  liquid  fuel     ......  112 

26.  Korting's  liquid  fuel  burning  apparatus    .......  113 

27.  ,,  ,,         ,,     applied  to  a  Lanes,  boiler                    ....  113 

28.  Meldrum's  interlocking  fire  bars  for  burning  refuse  fuel    ....  115 

29.  Sectional  drawings  of  Messrs.  Meldrum's  low-grade  fuel  furnace         .          .  116 

30.  Sections  of  Lanes,  boiler  fitted  with  Proctor's  shovel  mechanical  stoker     .  117 

31.  Sections  of  Henderson's  mechanical  stoker        ......  118 

32.  Section  of  ram  and  hopper  of  Meldrum's  coker  stoker        ....  119 
33Y  Mechanism  of  Wilkinson  mechanical  stoker     ......  120 

34.  Sections  of  Hodgkinson's  mechanical  stoker     ......  121 

35.  Section  of  a  mechanical  stoker         ........  121 

36.  Sections  of  the  "  Auto  "  stoker         ........  122 

37.  Section  of  Lanes,  boiler  fitted  with  Vicars  mechanical  stoker    .         .          .  124 

38.  Section  of  Underfeed  mechanical  stoker  ......          .  125 

39.  Section  of  Underfeed  stoker,  showing  the  ram 126 


xiv  LIST   OF   ILLUSTRATIONS 

FIG.  PAGE 

40.  Diagram  showing  course  of  air  and  hot  gases,  with  forced  draught  and  an 

economizer.          ...........  140 

41.  Diagram  showing  course  of  air  and  hot  gases  in  a  Lanes,  or  Cornish  boiler 

with  induced  draught  and  an  economizer       ......  142 

42  and  43.     Sections  of  Ellis  and  Eaves  system  of  air-heating  for  marine  boilers  144 

44.  Section  of  Lanes,  boiler,  fitted  with  Meldrum's  fire  bars  and  steam  jet       .  148 

45.  Automatic   Hydraulic   damper  regulator,  made   by  Messrs.   Fraser   and 

Chalmers 150 

46.  Complete  steam  gauge  with  dial  and  needle      ......  152 

47.  Steam  gauge  shown  in  Fig.  46,  with  dial  removed 152 

48.  Sections  of  Lanes,  boiler,  with  Hopkinson's  flue        .....  153 

49.  Section  of  Eaves'  dead- weight  safty  valve          ......  154 

50.  Section  of  high-steam  pressure  and  low- water  safety  valve         .          .          .  156 

51.  Elevation  of  Green's  economizer      ........  157 

52.  Sectional  plan  of  Green's  economizer        .......  157 

53.  Section  of  Green's  economizer,  showing  tubes  and  enclosing  brickwork       .  158 

54.  Plan  of  three  Lanes,  boilers,  with  Green's  economizers     ....  159 

55.  Elevation   and   plan  of    scrapers   employed   by  Messrs.  Green    on   their 

economizers         ...........  160 

56.  Eiblet  steam  feed- water  heater         ........  164 

57.  Hardwick  steam  feed-water  heater  .          .          .          .          .          .          .         .164 

58.  R-oyle's  feed-water  heater         .                   .......  165 

59.  Vertical  transverse  section  of  Messrs.  Royle's  feed-water  heater          .          .  165 

60.  Wainwright's  curves  for  the  relative  heating  effect   .....  167 

61.  Messrs.  Holden  and  Brooke's  live  steam  feed-water  heater         .          .          .  167 

62.  Diagram  showing  course  of  steam  and  water,  where  condensed  steam  is 

employed  for  boiler  feed       .........  169 

63.  Diagram  showing  arrangement  where  circulating  water  from  condenser  is 

employed  as  feed-water  for  boiler          .......  169 

64.  Sectional  drawing  of  reverbatory  steam  injector        .....  174 

65.  Section  of  Messrs.  Davies  and  Metcalfe's  injector 174 

66.  Section  of  Messrs.  Holden  and  Brooke's  injector,  for  live  steam  and  exhaust 

steam 175 

67.  Messrs.  Holden  and  Brooke's  injector  for  exhaust  steam   ....  175 

68.  Section  of  Criton  water  softener      ........  185 

69.  Vertical  type  of  Bruun  Lowener  water  softener         .....  187 

70.  Mixing  portion  of  Doulton's  water  softener      ......  189 

71.  Section  of  Desrumeaux  water  softener      .......  190 

72.  Diagram  showing  course  of  water  to  be  purified  in  the  Harris-Anderson 

apparatus  ............  193 

73.  Drawing  showing  Harris-Anderson  water  purifying  apparatus  .         .         .  194 

74.  Sections  of  Reid's  oil  separator 196 

75.  Messrs.  Holden  and  Brooke's  exhaust  head       ......  197 

76.  Diagram  of  Davis-Perrett's  electrical  emulsifier 198 

77.  Tinker's  superheater,  as  fitted  to  a  Lanes,  boiler       .....  201 

78.  Schmidt's  superheater  arranged  for  heating  by  boiler  flue  gases         .          .  202 

79.  Sections  of  Schmidt's  superheater  arranged  for  direct  firing      .          .          .  202 

80.  The  Sims  steam  separator,  for  fixing  in  a  horizontal  pipe ....  204 

81.  Sectional  drawing  of  Weir's  vertical  evaporator         .                    .          .          .  206 

82.  Curve  showing  percentage  of  fuel  lost,  with  different  percentages  of  C02, 

in  the  flue  gases  ...........  207 

83.  Sectional  elevation  of  "  Sarco  "  flue  gas-testing  apparatus,  made  by  Messrs. 

Sanders,  Rehder,  and  Co 209 

84.  Diagram  of  Simmance  and  Abady  flue  gas-testing  apparatus      .          .          .  210 

85.  Charts  taken  by  Simmance  and  Abady's  flue  gas-testing  apparatus     .          .  211 

86.  Diagram  showing  course  of  steam,  with  non-condensing  simple  engine       .  221 

87.  Diagram  showing  course  of  steam  in  a  non-condensing  compound  engine  .  221 

88.  Single-cylinder  wall  engine,  made  by  Messrs.  Ransome,  Sims,  and  Jeffries  .  222 

89.  Single-cylinder  horizontal  engine  with  vertical  boiler,  made  by  H.  Coltman 

and  Sons .  223 


LIST   OF   ILLUSTRATIONS  xv 

FIG.  PAGE 

90.  Section  of  tandem  compound  engine,  without  receiver  between        .          .  223 

91.  Horizontal  tandem  compound  condensing  engine,  made  by  E.  B.  and  F. 

Turner 224 

92.  Horizontal  cross-compound  condensing  engine,  made  by  Bansome,  Sims, 

and  Co 224 

93.  Compound  vertical  engine,  unenclosed,  with  shaft  governor     .          .         .  225 

94.  Diagram  of  course  of  steam  in  a  non-condensing  triple  expansion  engine  226 

95.  Sections  of  Allen's  enclosed  high-speed  engines       .          .          .          .          .  229 

96.  Sections  of  compound  Belliss  high-speed  enclosed  engine         .          .          .  230 

97.  Sections  of  Browett-Lindley  compound  high-speed  enclosed  engine .          .  230 

98.  Section  of  Bumsted  double-acting  compound  enclosed  engine            .          .  236 

99.  Section  of  Peache  high-speed  single-acting  enclosed  engine      .         .          .  237 

100.  Section  of  cylinder  of  Lanes,  mill  engine,  with  "  Wheelock  "  valves         .  241 

101.  Section  of  one  form  of  slide  valve  ........  244 

102.  Section  of  another  form  of  slide  valve 244 

103.  Section  of  cylinder  with  drop  valve,  made  by  Messrs.  Marshall         .          .  250 

104.  Cylinder  with  drop  valves  and  trip  gear           ......  250 

105.  Corliss  valves  with  wrist  plate,  made  by  Fulton  Co.,  of  America       .          .  251 

106.  Section  of  single  cylinder  engine,  with  Corliss  valves,  made  by  Atlas  Co.  .  252 

107.  Double  cylinder  Corliss  engine  made  by  Fishkill  Co.        ....  253 

108.  One  form  of  stop  valve,  made  by  W.  H.  Willcox 254 

109.  Section  of  stop  valve,  made  by  Messes.  Alley  and  Maclellan    .          .          .  255 

110.  Section  of  throttle  valve,  made  by  Messrs.  Alley  and  Maclellan        .          .  255 

111.  Hopkinson's  parallel  slide  stop  valve       .......  256 

112.  Hopkinson's  centre  pressure  valve,  shut           .          .          .          .         .          .  258 

113.  „                „                „                ,  partly  open 258 

114.  „                ,,                ,,                ,  full  open 258 

115.  Valve  for  reducing  pressure  of  steam       ...                   ...  259 

116.  Pickering  governor        ..........  265 

117.  Section  of  Proell's  governor  .........  266 

118.  Wilson  Hartnell's  expansion  governor    .......  267 

119.  Expansion  governor  made  by  Messrs.  Coltrnan        .                   ...  268 

120.  Proell  governor,  fixed  on  end  of  crank  shaft    ......  269 

121.  Expansion  shaft  governor  for  high-speed  vertical  engines         .          .          .  269 

122.  Crosby's  steam-engine  indicator     .          .          .          .          .          .          .  270 

123.  Examples  of  indicator  cards  taken  from  triple  expansion  engine      .          .  271 

124.  One  form  of  planimeter  made  by  Messrs.  Crosby    .....  272 

125.  Another  form  of  Planimeter,  ditto,  ditto         .....  272 

126.  "  Wedgring  "  coupling  for  steam  pipes   .......  280 

127.  Sectional  view  of  Brooke  steam  trap       ......  281 

128.  Section  of  discharge  end  of  Brooke  steam  trap         .....  281 

129.  Inside  view  of  "  Sirius "  steam  trap        .....  282 

130.  Longitudinal  section  of  Lancaster  steam  trap          .....  283 

131.  Transverse  vertical  section  of  Lancaster  steam  trap         ....  284 

132.  Section  of  Parsons  turbine    .........  293 

133.  Willans'  arrangement  of  rotor  and  stator  blades 293 

134.  Section  of  Willans-Parsons  steam  turbine      ......  295 

135.  Section  of  Parsons  turbine     .......  296 

136.  Sectional  drawing  of  Parsons  steam-turbine  governor     .          .          .  297 

137.  Parsons  turbo  pump      ........  298 

138.  Cross  section  and  plan  of  Parsons  turbines  for  steamship  propellers          .  299 

139.  Section  of  nozzle  of  De  Laval  turbine    .....  302 

140.  Governor  of  De  Laval  turbine        ......  304 

141.  Section  of  steam  valve  controlled  by  governor         .          .  304 

142.  Sectional  plan  of  De  Laval  turbine         .....  306 

143.  De  Laval  turbine  directly  connected  to  a  turbine  pump  307 

144.  Parts  of  the  De  Laval  turbine        .....  307 

145.  Section  of  part  of  Curtis  turbine,  showing  two  stages      .  310 

146.  Sectional  elevation  of  Curtis  turbine      ....  312 

147.  Elevation   of  a  part   of   an  electricity  generating  station  with   Curtis 

turbine,  etc.      ........  314 


xvi  LIST   OF   ILLUSTRATIONS 

FIG.  PAGE 

148.  Plan  of  portion  of  electricity  generating  station      .....  314 

149.  Section  of  one  form  of  Bateau  turbine    .......  315 

150.  Section  of  one  form  of  the  A.E.G.  steam  turbine    .....  317 

151.  Drawing  of  Zoelly  turbine 318 

152.  Runner  of  Zoelly  steam  turbine,  in  plan  and  elevation    ....  319 

153.  Stationary  blade  of  Zoelly  turbine 319 

154.  Governor  of  Zoelly  turbine   .........  320 

155.  One  form  of  Prof.  Bateau's  apparatus  for  storing  heat     ....  323 
156. .  Another  form  of  Bateau's  heat-storage  apparatus    .....  324 

157.  Diagram  of  steam  plant  at  Bruay  Colliery,  Pas  de  Calais         .          .          .  326 

158.  Sectional  drawing  of  surface  condenser  and  cooling  tower        .         .          .  333 

159.  Ledward's  evaporative  surface  condenser        ......  334 

160.  Wheeler  surface  condenser 337 

161.  Sectional  drawings  of  Contrafio  condenser      ...          .          .          .          .  338 

162.  Section  of  Worthington  jet  condenser  and  pump    .....  341 

163.  Worthington  jet  condenser  for  1500  H.P.  with  pump      ....  342 

164.  Section  of  Ledward  ejector  condenser     .......  343 

165.  Diagram  of  steam  and  water  pipes,  with  Ledward's  ejector  condenser       .  344 

166.  Arrangement  of  pipes,  pumps,  etc.,  of  Bulkley  barometric  condenser        .  345 

167.  Sectional  diagram  of  barometric  tube  condenser     .....  346 

168.  Section  of  Parsons  vacuum  augmenter  .......  347 

169.  Plan  and  vertical  section  of  central  condensing  plant,  with  cooling  tower  350 

170.  Allen's  curves  showing  steam  and  coal  consumption,  etc.,  with  different 

vacua       .                   ..........  353 

171.  Allen's  curves  showing  steam  and  coal  consumption        ....  354 

172.  Allen's  curves  showing  coal  saved,  consumption  of  steam  and  condensing 

plant,  etc.         ............  355 

173.  Allen's  curves  showing  quantities  of  circulating  water,  with  different  vacua  357 
174  and  175.     Curves  showing  different  quantities  of  circulating  water     .          .  358 
176  and  177.     Curves  similar  to  Figs.  174  and  175 359 

178.  Curves  showing  results  of  Prof.  Weighton's  experiments          .          .          .  362 

179.  Curves  showing  results  of  Prof.  Weighton's  experiments          .          .          .  362 

180.  Curves  showing  cost  in  H.P.  in  circulating  cooling  water        .          .          .  364 

181.  Curves  showing  Prof.  Weighton's  experiments        .....  364 

182.  Section  of  Edwards  air  pump        ........  366 

188.  Diagram  of  course  of  water  when  cooling  tower  is  used  ....  368 

184.  Cooling  tower  for  wind  draught    ........  371 

185.  Section  of  chimney  cooling  tower  .......  373 

186.  Barnard  chimney  cooling  tower    .          .          .          .         .         .         .          .  373 

187.  Another  form  of  Barnard  chimney  cooling  tower    .....  374 

188.  Balcke  fan-cooling  tower       .........  376 

189.  Worthington  fan-cooling  tower     ........  378 


LIST   OF  PLATES 


PLATE                                                                                                                                                                                                         TO   FACE  PAGE 

Modern  electricity  generating  station,  with  Marshall's  cross  compound 
condensing  engines     ........       Frontispiece. 

IA.  Galloway  Cornish  boiler,  with  cone  tubes        ......  48 

IB.  Battery  of  Lancashire  boilers,  Rushton,  Proctor  and  Co.          ...  48 

2A.  Galloway  Lancashire  boiler,  with  cone  tubes           .....  64 

2B.  Battery  of  Galloway  Lancashire  boilers,  adapted  for  burning  low  grade 

fuel .  64 

2c.  Galloway  multitubular  boiler,  with  external  firing  .....  64 

SA.  Galloway  boiler  arranged  for  burning  wood    ......  72 

SB.  Atlas  externally  fired  multitubular  boiler        ......  72 

3c.  Locomotive  type  of  boiler,  by  Messrs.  Marshall       .....  72 

4A.  Three  furnace  marine  boiler,  by  Central  Engineering  Works  ...  80 

4s.  Thornycroft  water-tube  boilers       ........  80 

5A.  Babcock  water-tube  boiler     .........  88 

5B.  Marshall  water-tube  boiler     .........  88 

6A.  Atlas  water-tube  boiler           .........  96 

6s.  White  boiler  for  steam  cars  .........  96 

7A.  Meldrum's  low-grade  fuel  furnace           .......  112 

7B.  Water-tube  boiler  fitted  with  chain-grate  stokers              .          .          .          .  112 

SA.  Proctor's  mechanical  stoker            ........  128 

SB.  Babcock 's  chain-grate  stoker  (front) 128 

8c.  „  „  „  (back) .128 

9A.  Hoppes'  feed-water  heater,  and  purifier 160 

9B.  Deposit  from  Hoppes'  feed-water  heater          ......  160 

9c.  Hoppes'  apparatus  fitted  to  water-tube  boiler 160 

10A.  Evaporator  by  Central  Engineering  Works     ......  176 

10B.  Tangye  single  cylinder  horizontal  engine 176 

lOc.  Marshall's  single  cylinder  horizontal  engine   ......  176  ' 

10D.  Tangye  single  cylinder  vertical  engine  .......  176 

HA.  Huston's  compound  engine,  tandem,  with  trip  gear          ....  192 

HB.  Ditto            „             „                                                              ....  192 

He.  Ditto            „            „            „             „            „ 192 

12.  Adamson's  Lancashire  mill  engine,  horizontal,  triple  expansion       .          .  208 

13A.  Galloway's  vertical  cross  compound  engine     .          .                   ...  224 

13s.  Marshall's  cross  compound  engine,  horizontal          .....  224 

13c.  Marshall's  tandem  compound  engine,  horizontal     .....  224 

14A.  Huston's  tandem  compound  horizontal  engine         .....  232 

14s.  Marshall's  coupled  compound  condensing  engine,  with  rope    drive    to 

dynamo 232 

15A.  Triple  expansion  marine  engine  by  Central  Engineering  Works        .          .  240 

15s.  Single  cylinder  Corliss  engine,  by  Atlas  Co.    ......  240 

15c.  Vertical  compound  enclosed  engine  with  steam  separator         .          .          .  248 

16.  Bumsted  single  cylinder  vertical  encased  engine     .....  248 

17A.  Horizontal  cross-compound  engine,  with  rope  drive,  for  Lancashire  mills  256 

xvii 


xviii  LIST   OF   PLATES 

PLATE  PAGE 

17s.  Trip  valve  gear  and  governor,  made  by  Easton  and  Bessemer  .  .  .  256 

ISA.  Eotor  of  Brush-Parsons'  steam  turbine 280 

18B.  Half  of  stator  of  Brush-Parsons'  turbine 280 

18c.  Brush-Parsons'  turbine,  connected  to  alternator  and  its  excitor  .  .  280 
19 A.  Parsons'  turbine,  with  steam  and  oil  connections,  etc.  by  Richardson  and 

Westgarth 288 

19s.  Richardson's  Westgarth-Parsons'  steam  turbine,  from  steam  end  .  .  288 

19c.  Richardson's  Westgarth-Parsons'  steam  turbine,  from  generator  end  .  288 

20A.  De  Laval  turbine,  with  gearing  and  pulleys  by  Greenwood  and  Batley  .  296 
20B.  De  Laval  turbine,  with  gearing  directly  connected  to  a  150  H.P.  De  Laval 

turbine  pump   ...........  296 

2lA.     De  Laval  turbine  connected  to  a  60  H.P.  De  Laval  turbine  pump    .          .  304 

2lB.     De  Laval  turbine  connected  to  De  Laval  15  H.P.  turbine  pump       .          .  304 

22A.     De  Laval  turbine  directly  connected  to  a  fan  .....  312 

22B,     A  Zoelly  turbine,  made  by  Escher,  Wyss,  and  Co.  .  ...  312 

23A.     Complete  Contraflo  condenser        ........  328 

23s.     Contraflo  condenser,  with  air  pump        .......  328 

24A.     Condensing  plant  for  a  pair  of  blowing  engines       .....  336 

24s.     Tangye  duplex  double-acting  steam  pump       ......  336 

25A.  Pair  of  vertical  double-acting  pumps,  by  Mirrlees  Watson  Co.  .  .  344 

25B.  Hall's  vertical  duplex  steam  pump 344 

25c.  Surface  condenser,  with  two-cylinder  Edwards'  air  pump  .  .  .  344 

25D.  Hall's  single  vertical  steam  pump 344 

26A.  Two-stage  horizontal  steam-driven  slide-valve  dry-air  pump,  by  Mirrlees 

Watson  Co 352 

26B.  Two-throw  steam-driven  slide-valve  dry-air  pumps,  by  Mirrlees  Watson  Co.  352 

26c.  Three-throw  Edwards'  air  pump,  electrically  driven  ....  352 

27 A.  Single-throw  vertical  Edwards'  air  pump,  by  Mirrlees  Watson  Co.  .  .  368 

27B.  Three-throw  vertical  Edwards'  air  pump,  by  Mirrlees  Watson  Co.  .  .  368 

27c.  Mirrlees  Watson  surface  condensing  plant 368 


STEAM    BOILERS,    ENGINES, 
AND    TURBINES 


CHAPTER  I 

INTRODUCTORY 
What  Heat  is 

ACCORDING  to  the  latest  theory,  and  the  only  one  so  far  as  the  author 
is  aware  that  is  at  present  in  vogue,  what  we  know  as  heat  is  a 
wave  motion  in  the  ether.  The  theory  is  known  sometimes  as  the 
mechanical  theory  of  heat,  and  sometimes  as  the  wave  theory. 

Every  one  is  familiar  with  the  experiment  that  is  mentioned  in 
heat  and  light  text-books,  of  a  boy  throwing  a  stone  in  the  water,  and 
the  circles  of  waves  which  follow.  Most  of  us  also  have  watched  the 
waves  which  are  pushed  out  from  the  bow  of  a  steamer,  as  it  cleaves 
its  way  through  the  water.  We  have  also,  most  of  us,  sat  on  the  sea- 
shore and  watched  the  waves  come  rippling  up,  one  after  the  other, 
at  our  feet.  We  notice  two  or  three  characteristics  about  the  circular 
waves.  They  are  continually  moving  onward,  and  in  the  case  of  the 
waves  created  by  a  stone  thrown  in  the  water,  with  ever  increasing 
diameter  and  ever  decreasing  force.  We  notice  also  that  as  a  wave 
moves  onward,  the  water  rises  as  the  wave  meets  it,  falling  afterwards, 
rising  with  the  next  wave,  and  so  on,  and  we  may  notice  that  the 
water  through  which  the  wave  passes,  does  not  move  on,  though  the 
wave  does.  A  cork  floating  on  the  water  bobs  up  and  down,  as  it 
forms  the  crest  or  the  trough  of  the  wave,  but  remains  practically 
stationary,  unless  it  is  carried  on  by  a  tide  or  river  current. 

The  Ether 

The  ether  is  the  substance  which  is  supposed  by  scientists  to 
pervade  all  space.  It  is  the  substance,  the  sea  it  may  be  termed,  in 


2        STEAM   BOILERS,    ENGINES,   AND   TURBINES 

which  our  earth,  our  sun  and  the  other  planets,  and  the  other  worlds 
we  call  heavenly  bodies,  are  all  floating.  Further,  the  ether  is  all 
pervading.  It  not  only  fills  the  space  between  the  planetary  and 
other  celestial  bodies,  but  it  is  present  in  every  substance.  Every 
substance,  as  we  know,  is  more  or  less  porous.  We  are  familiar  with 
the  fact  that  a  sponge  holds  water  in  its  pores.  All  substances,  and 
all  bodies,  are  porous  in  a  similar  sense,  to  the  ether.  The  waves  by 
which  heat  is  transmitted,  and  the  waves  by  which  the  presence  of  heat 
is  denoted,  pass  through  the  ether,  not  only  in  coming  from  the  sun 
to  us,  but  in  the  ether  held  in  every  substance.  Thus,  when  we  say 
that  a  body  is  heated  to  a  certain  temperature,  as  the  author  under- 
stands it,  we  mean  that  a  certain  wave  motion  is  going  on  in  the 
ether  held  in  the  ethereal  pores  of  that  body.  According  to  the 
modern  view,  all  heat  comes  to  us  from  the  sun.  The  earth  itself 
contains  a  certain  quantity  of  heat  in  its  substance,  but  this  also 
originally  came  from  the  sun,  inasmuch  as  modern  views  suppose  that 
the  earth  and  the  other  planets  originally  formed  parts  of  the  body  of 
the  sun,  and  were  thrown  out  by  him  at  various  times,  the  different 
portions  that  have  since  become  different  planets  having  gradually 
cooled  as  they  whirled  through  space.  A  certain  quantity  of  heat 
reaches  us  from  the  other  planets  of  the  solar  system,  and  from  the 
myriads  of  other  worlds  to  be  seen  through  a  telescope,  and  the  other 
myriads  that  are  still  invisible  to  the  most  powerful  telescope ;  but 
the  sum  of  the  heat  which  reaches  us  from  all  of  these  is  but  a  small 
fraction  of  that  coming  to  us  daily  from  the  sun,  and  we  may  there- 
fore say  that,  for  practical  purposes,  all  heat  comes  to  us  from  the  sun. 

Properties  of  Heat  Waves 

Heat  waves  have  certain  properties,  and  they  are  closely  allied 
to  light  waves.  If  we  take  a  diagram  of  the  spectrum,  in  which 
the  lengths  of  the  waves  of  heat  and  different  forms  of  light  are 
shown,  we  shall  notice  that  heat  waves  are  longer  than  light 
waves,  but  in  every  other  respect  they  are  similar.  What  appears 
to  our  senses  as  white  light,  as  we  know,  is  made  up  of  a  number 
of  colours,  as  shown  in  the  rainbow,  and  that  can  be  produced 
by  passing  a  ray  of  light  through  a  glass  prism.  As  we  know, 
in  the  rainbow  and  in  the  spectrum  produced  by  the  glass  prism, 
the  prismatic  colours,  as  they  are  called,  run  from  left  to  right  as 
follows.  Ked  on  the  extreme  left,  violet  on  the  extreme  right,  yellow 
in  the  middle,  orange,  green,  blue  occupying  intermediate  positions. 
The  wave  lengths  of  the  red  rays  are  approximately  twice  that  of  the 
violet  rays,  and  consequently  the  rate  of  motion  of  the  violet  rays  is 
twice  that  of  the  red  rays.  The  figures  are  -^^Q  inch  for  the  red 
rays,  and  6eoo~o  ^ncn  f°r  the  violet  rays.  Outside  of  the  red  rays, 


INTRODUCTORY  3 

still  further  to  the  left  of  the  spectrum,  heat  rays  are  present,  known 
sometimes  as  the  infra  red  rays,  and  sometimes  as  the  dark  or  invisible 
rays.  They  are  the  heat  rays  of  which  we  are  sensible  when  emanating 
from  a  black  heated  body,  such  as  a  hot  kettle,  or  saucepan,  or  poker. 
The  waves  of  these  rays  are  longer  than  the  red  rays,  and  have  a 
slower  rate.  To  the  right  again  of  the  violet  rays,  there  is  another 
large  space  occupied  by  invisible  rays,  whose  wave  length  is  shorter 
than  that  of  the  violet,  and  whose  period  is  higher.  These  waves  are 
known  as  the  actinic,  or  chemical  rays,  from  the  properties  which 
they  possess.  It  is  the  violet  and  the  ultra  violet  rays,  as  they  are 
sometimes  called,  that  are  so  useful  in  photography,  and  that  are  so 
troublesome  to  the  housekeeper  at  times  in  destroying  the  colours  of 
fabrics  used  in  furniture.  The  waves  comprised  in  the  whole  range 
of  the  spectrum,  and  the  portions  mentioned  beyond  the  spectrum, 
have  other  important  properties.  They  are  capable  of  reflection, 
refraction,  and  polarization. 

We  all  know  what  is  meant  by  reflection.  We  all  make  use  of 
it  when  we  look  in  a  mirror.  The  light  rays  impinge  on  our  bodies, 
are  reflected  from  them  to  the  mirror,  and  reflected  out  again  to  our 
eyes,  and  we  see  the  reflected  image  of  ourselves  in  the  mirror. 
Light  rays  are  reflected  by  plane  mirrors  in  this  manner,  and  in 
accordance  with  a  certain  law,  viz.  the  angle  of  incidence  =  the  angle 
of  reflection.  That  is  to  say,  the  angle  which  the  impinging  ray 
makes  with  the  plane  of  the  mirror  is  equal  to  the  angle  which  the 
ray  passing  out  makes  with  it. 

Heat  rays  are  reflected  by  plain  metallic  and  certain  other  sub- 
stances, in  the  same  manner  as  light  rays  are  reflected  by  mirrors, 
and  follow  the  same  laws. 

Heat  and  light  rays  are  also  reflected  by  curved  surfaces,  the 
reflections  following  the  same  law  that  has  been  given  above,  the 
angle  of  incidence  being  equal  to  the  angle  of  reflection,  and  this 
leads  to  the  divergent  rays  impinging  upon  concave  surfaces  being 
brought  together  in  one  point  known  as  the  focus.  This  fact  is  of 
importance  in  certain  cases. 

Heat  and  light  rays  are  also  refracted.  That  is  to  say,  they  are 
bent  in  passing  through  different  substances.  Every  substance  offers 
a  certain  resistance  to  the  passage  of  both  heat  and  light  rays,  and 
this  resistance  apparently  leads  to  alteration  in  the  direction  of  the 
rays  in  different  media.  The  alteration  in  the  direction  or  the 
bending  is  different  for  the  different  waves.  The  waves  of  shorter 
length  are  bent  less.  The  law  is  as  follows.  The  incident  and 
refracted  rays  are  in  the  same  plane  as  a  normal  to  the  surface  upon 
which  the  ray  impinges,  and  the  sines  of  the  angles  of  inclination  of 
the  two  rays  are  in  a  constant  ratio,  for  the  same  wave  length,  and 
the  same  media.  This  constant  ratio  is  called  the  refractive  index. 


4        STEAM    BOILERS,   ENGINES,   AND   TURBINES 

When  a  ray  of  heat  or  light  passes  from  a  rarer  into  a  denser  medium, 
the  angle  of  refraction,  the  angle  which  the  refracted  ray  makes  with 
the  normal  to  the  common  surface  is  less  than  the  angle  of  inci- 
dence, the  angle  which  the  impinging  ray  makes  with  the  normal  to 
the  surface,  and  vice  versa. 

Polarization  need  not  trouble  us  ;  it  merely  means  the  property 
which  certain  crystals  have,  when  cut  in  a  certain  way,  of  stopping 
certain  rays.  The  only  point  to  note  is  that  all  the  properties  of 
reflection  and  polarization  are  common  to  both  heat  and  light  rays. 

Temperature 

Temperature  is  in  heat,  what  pressure  is  in  mechanics,  and  in 
electricity.  Heat  passes  from  a  higher  to  a  lower  temperature,  just 
as  electricity  does  from  a  higher  to  a  lower  pressure,  and  just  as 
a  weight  falls  from  a  higher  to  a  lower  level.  There  are  three 
scales  by  which  heat  is  measured,  known  respectively  as  the 
Fahrenheit,  Centigrade,  and  Eeaumur.  The  Eeaumur  scale  is  not 
now  often  seen  or  used  in  calculations,  but  Fahrenheit  and  Centi- 
grade are  in  constant  use.  The  Fahrenheit  may  be  taken  to  be 
the  scale  employed  more  in  everyday  life;  the  Centigrade,  that 
used  in  scientific  calculations.  The  Centigrade  thermometer  is 
also  sometimes  known  as  the  Celsius — Celsius,  Fahrenheit,  and 
Eeaumur  being  the  introducers  of  the  respective  scales.  All  of  the 
scales  are  based  upon  two  well-known  fixed  points  of  temperature, 
viz.  that  at  which  ice  commences  to  melt  into  water,  and  that  at 
which  water  commences  to  form  steam,  both  being  at  the  barometric 
pressure,  29'96  inches,  that  is  used  in  all  standard  calculations,  and  at 
sea-level.  As  will  be  seen  later,  the  boiling-point  of  water,  the  tempe- 
rature at  which  it  commences  to  form  steam,  varies  with  the  pressure 
to  which  it  is  subject.  In  the  Centigrade  scale,  the  temperature  at 
which  ice  commences  to  melt,  or  the  freezing-point  of  water,  as  it  is 
usually  expressed,  is  taken  (as  0°,  and  the  temperature  at  which 
steam  commences  to  form  water  is  taken  at  100° ;  hence  the  name  of 
the  scale.  In  the  Fahrenheit  scale,  the  freezing-point  of  water  is 
taken  at  32°,  and  the  boiling-point  of  water  at  212°.  In  the  Eeaumur 
scale,  the  freezing-point  is  taken  as  0°,  and  the  boiling-point  as  80°. 
In  each  of  the  scales  the  intervals  between  the  two  points  are  equally 
divided — in  the  Centigrade  into  100  parts,  in  the  Fahrenheit  into  180 
— the  scale  being  extended  downwards  to  0 — and  in  the  Eeaumur 
into  80,  each  division  in  each  scale  being  called  a  degree,  though 
neither  of  the  divisions  of  the  thermometric  scales  have  any  connec- 
tion with  the  divisions  of  a  circle,  which  are  also,  it  will  be  remem- 
bered, called  degrees. 


INTRODUCTORY 


Absolute  Temperature 

As  will  be  seen  when  dealing  with  air  and  other  gases,  it  is  found 
that  gases  expand  and  contract  at  a  certain  definite  rate  for  each 
degree  of  rise  or  fall  of  temperature,  such  that  at  a  certain  number  of 
degrees  below  the  freezing-point  of  water,  if  it  could  be  produced, 
they  would  cease  to  exist,  the  volume  being  nil.  This  point,  which 
is  273°  below  0°  on  the  Centigrade  scale,  or  -  273°  C.,  and  493°  on  the 
Fahrenheit  scale  below  freezing-point,  or  461°  below  0°,  or  —  461°  F., 
is  known  as  the  absolute  zero,  and  all  calculations  are  made  from  this 
point.  In  dealing  with  the  working  of  gases,  steam,  etc.,  it  will  very 
often  be  necessary  to  refer  to  the  absolute  temperatures,  as  the  expan- 
sions and  contractions,  the  passages  of  heat  from  point  to  point,  and 
from  surface  to  surface  are  controlled  by  the  difference  in  the  absolute 
temperature.  The  absolute  temperature  is  found  in  the  two  scales 
by  adding  273  for  Centigrade  and  461  for  Fahrenheit,  to  the  readings 
of  the  scale.  The  following  formulae  will  be  useful  for  converting 
Centigrade  temperatures  to  Fahrenheit,  and  Fahrenheit  to  Centi- 
grade :• — 

F.  =  1-8  C.  +  32  C.  =  (j)  F.  -  32 

where  C.  is  the  number  of  degrees  Centigrade  and  F.  the  number 
Fahrenheit. 

Measurement  of  Temperatures 

For  measurement  of  the  lower  temperatures,  the  mercurial  ther- 
mometer, made  in  various  forms,  is  sufficient,  but  for  higher  tempera- 
tures than  500°  F.,  special  forms  of  apparatus  have  to  be  employed, 
and  in  boiler  work  temperatures  as  high  as  3000°  F.  may  have  to  be 
measured.  The  mercurial  thermometer  made  for  ordinary  domestic 
use  is  rarely  arranged  to  read  temperatures  above  120°.  It  is  only 
used  for  indicating  the  temperature  of  the  air  of  rooms,  or  of  water 
for  baths.  For  Turkish  baths  and  for  the  temperatures  of  boiling 
water  under  ordinary  atmospheric  pressure,  the  Fahrenheit,  or  prefer- 
ably the  Centigrade  thermometer,  graduated  to  a  few  degrees  above 
boiling-point,  answer  all  purposes.  For  higher  temperatures  again, 
up  to  500°  F.,  the  Centigrade  thermometer  having  a  scale  graduated 
up  to  500°  will  answer  the  purpose.  But  mercury  boils  at  676°  C., 
and  at  temperatures  over  500°  C.  it  is  unsuitable  for  measurements, 
unless  special  arrangements  are  made.  It  can  still  be  employed  for 
temperatures  up  to  800°  F.  by  the  employment  of  a  simple  device, 
the  utility  of  which  will  be  recognized  from  what  is  said  later  in  the 
book,  about  boiling-points  and  pressures  to  which  the  surfaces  of 
the  liquids  are  exposed.  For  the  higher  temperature  mercurial 


6        STEAM   BOILERS,   ENGINES,   AND   TURBINES 

thermometer,  a  certan  quantity  of  nitrogen  gas  is  included  in  the  tube 
above  the  mercury.  Nitrogen,  it  will  be  remembered,  has  no  chemical 
effect  upon  mercury.  As  the  mercury  rises,  when  expanding  in  the 
presence  of  heat,  the  rising  column  compresses  the  nitrogen  gas  above 
it,  and  producing  thereby  a  gradually  increasing  pressure  upon  the 
surface  of  the  mercury,  raises  the  boiling-point  of  the  latter,  and  so 
enables  mercury  to  be 'employed  up  to  800°  F.  After  800°  F.  there 
are  three  methods  that  may  be  employed — the  melting-points  of 
different  substances,  the  expansion  pyrometer,  and  the  thermo-electric 
pyrometer.  In  the  following  table  the  melting-points  of  different 
substances  employed  in  the  measurement  of  temperatures  is  given, 
and  makers  of  thermometric  and  pyrometric  apparatus  supply  sets 
of  the  substances,  arranged  in  convenient  forms  for  placing  in  the 
path  of  the  gases  or  air,  or  in  the  space  whose  temperature  is  to  be 
measured. 


TABLE  I. 
APPROXIMATE  MELTING-POINTS  OF  METALS  (STIRLING  BOILER  Co.). 

Wrought  iron  melts  at  about  2825°  Fahr. 

Steel  (low  carbon)  2600° 

„     (high  carbon)  2400° 

Cast  iron  (white)  2200° 

(grey)  2000° 

Copper  1975° 

Gun-metal  1700° 

Zinc  764° 

Antimony  940° 

Lead  618° 

Bismuth  514° 

Tin  447° 

Platinum  3230° 

Gold  2056° 

Silver  1788° 

Aluminium  1172°. 


The   Expansion   Pyrometer 

The  expansion  pyrometer  depends  upon  the  unequal  expansion  of 
brass  and  iron,  that  is  referred  to  in  dealing  with  the  expansion  of 
different  substances  in  the  presence  of  heat.  The  expansion  of  brass 
is  approximately  50  per  cent,  greater  than  that  of  iron,  the  coefficients 
of  linear  expansion  being  for  iron,  from  0-00000556  to  0'00000648,  and 
for  brass,  from  0-00000957  to  0*00001052.  With  low  temperatures, 
though  the  difference  in  the  rate  of  expansion  of  the  two  metals  some- 
times leads  to  inconvenience,  the  difference  in  any  small  length  of  the 
two  is  not  great,  but  with  high  temperatures  of  1500°  F.  and  above, 
the  difference  is  considerable,  and  this  fact  is  taken  advantage  of  in 
the  construction  of  the  expansion  pyrometer.  The  apparatus  consists 


INTRODUCTORY  7 

of  an  iron  pipe  closed  at  one  end,  and  having  a  brass  rod  held  inside 
the  pipe,  and  fixed  at  the  closed  end.  The  other  end  of  the  brass  rod 
is  free  to  move,  and  is  connected  to  multiplying  gear,  actuating  a 
pointer  moving  over  a  dial,  so  that  the  difference  in  the  expansion 
of  the  brass  and  iron,  which  measures  the  increase  of  temperature,  is 
read  off  on  the  graduated  dial,  the  dial  being  carefully  calibrated  for 
the  purpose.  The  apparatus  is  not  very  much  used,  as  it  requires 
considerable  skill,  and  is  somewhat  sluggish  in  action,  and  further, 
because  the  early  indications  obtained  from  it,  with  the  first  changes 
of  temperature,  are  in  the  reverse  direction  to  the  changes  of  heat 
actually  taking  place,  this  being  due  to  the  fact  that  the  iron  pipe 
shields  the  brass  rod  to  a  certain  extent — the  air  space  between  it 
and  the  brass  rod  being  a  bad  conductor,  the  iron  pipe  becomes  heated 
more  quickly  than  the  brass ;  and  on  the  other  hand,  it  cools  more 
quickly  than  the  brass  rod  when  the  temperature  is  falling,  for  the 
same  reason,  its  surface  being  directly  exposed  to  radiation. 

Thermo=electric   Pyrometers 

The  thermo-electric  pyrometer  is  rapidly  taking  the  place  of  all 
others,  for  the  measurement  of  all  ranges  of  temperature,  except 
those  that  are  conveniently  measured  by  the  mercurial  thermometer, 
and  for  which  no  particular  accuracy  is  required.  The  apparatus  is 
made  in  various  forms,  some  depending  on  the  principle  that  the 
electrical  resistance  offered  by  a  given  length  of  wire  of  a  particular 
metal,  increases  in  a  definite  ratio  with  every  degree  of  increase  of 
temperature;  and  others  upon  thermo-electricity.  For  the  resist- 
ance apparatus,  the  metal  usually  employed  is  platinum,  occasion- 
ally platinum  alloyed  with  iridium,  or  one  of  the  more  refractory 
metals.  It  will  be  understood  that  whatever  the  apparatus  employed 
is,  it  must  itself  be  able  to  withstand  the  highest  temperatures  it  is 
required  to  measure,  without  changing  its  physical  condition  in  such 
a  manner  as  to  vitiate  the  measurements.  A  short  length  of  a  fine 
platinum  or  platinum-iridium  wire  is  held  in  a  convenient  receptacle 
of  highly  refractory  material,  such  as  porcelain  that  has  been  fired  at 
a  very  high  temperature.  The  ends  of  the  platinum  wire  are  con- 
nected, outside  of  the  heat  zone,  to  copper  wires  leading  to  the  electrical 
measuring  apparatus.  The  measuring  apparatus  is  usually  arranged 
in  the  form  of  a  dial,  upon  which  the  temperatures  are  read  off  directly, 
a  pointer  moving  over  the  dial.  The  dial  is  really  a  galvanometer, 
forming  part  of  an  electric  circuit,  in  which  is  included  a  battery  of 
known  pressure  and  resistance.  The  instrument  is  calibrated  at  a 
certain  standard  temperature,  say  32°  F.,  the  temperature  of  melting 
ice.  As  the  temperature  to  which  the  platinum  wire  is  exposed 
increases,  the  resistance  of  the  platinum  wire  also  increases,  and  the 


8         STEAM   BOILERS,   ENGINES,   AND   TURBINES 


strength  of  the  current  passing  in  the  electric  circuit  and  through  the 
coils  of  the  galvanometer  decreases,  the  pointer  on  the  galvanometer 


.COUPLE 


PROTECTING  TUBE 


/I 
FURNACE  WALL 

FIG.  1. — Diagram  of  the  Connections  of  Crompton's  Thermo-Electric  Pyrometer. 
G  is  a  Tube  protecting  the  Thermo  Couple  of  Nickel  and  Steel,  a  Nickel  Eod 
being  inside  a  Steel  Tube,  but  not  touching  it.  The  two  are  connected  together 
at  the  fire  end  and  their  ends  connected  to  the  Circuit,  at  the  other  end.  N,  N,  N 
and  S,  S,  S  are  connecting  wires.  A  is  the  galvanometer. 

LEADS  TO 
INSTRUMENT 


FIG.  2. — Crompton's  Thermo-Electric  Pyrometer  arranged  to  be  inserted  in  a  Pocket 
in  a  Steam  Pipe,  to  take  the  Temperature  of  the  Steam  in  the  Pipe. 


LEADS  TO 
INSTRUMENT 


FURNACE 
OR 


FLUE 


332 


FIG.  3. — The  arrangement  of  Crompton's  Thermo-Electric  Pyrometer  for  taking  the 
Temperature  of  a  Furnace  or  Flue. 

moving  over  the  dial  in  unison  with  the  decrease  of  current  passing 
through  its  coils,  and  the  increase  of  temperature.    Convenient  points 


INTRODUCTORY 


are  taken,  say  at  212°,  300°,  400°  and  so  on,  up  to  the  highest  tempe- 
rature the  appartus  is  intended  to  measure.  In  the  thermo-electric 
apparatus  a  thermo-electric  couple  takes  the  place  of  the  resistance 
wire,  one  junction  being  in  the  refractory  tube,  and  the  other  outside. 
The  difference  of  electrical  pressure  created  in  the  couple  furnishes 


FIG.  4. — Bristol's  Thermo-Electric  Pyrometer  as  arranged  for  taking  the  Tempera- 
ture of  a  Bath  of  Metal,  or  a  Furnace  or  Flue. 

the  indications  of  temperature,  which  are  read  off  on  a  sensitive  volti- 
meter.  Fig.  1  is  a  diagram  of  the  connections  of  Crompton's  thermo- 
electric pyrometer.  Fig.  2  shows  the  apparatus  arranged  to  take  the 
temperature  in  a  steam  pipe,  and  Fig.  3  that  for  a  furnace  or  flue. 
Fig.  4  shows  the  Bristol  thermo-electric  pyrometer. 

Entropy 

The  term  "  entropy  "  has  only  been  introduced  within  recent  years, 
and  is  not  often  used  at  the  present  time  in  calculations,  except  in 
scientific  papers  and  articles.  The  author's  view  is  that  the  measure- 
ment of  heat  and  its  operation  has  not  sufficiently  advanced  to  enable 
much  use  to  be  made  of  entropy.  There  is  no  law  in  connection  with 
the  measurement  of  heat  similar  to  Ohm's  law  in  electricity.  Entropy, 
as  the  author  understands  it,  is  the  second  factor  required  to  make  up 
the  energy  expended,  transmitted,  or  transformed,  in  any  heat  operation. 
The  measurement  of  any  form  of  energy  requires  two  factors.  A 
weight  suspended  at  a  height  above  the  ground  is  possessed  of 
potential  energy,  in  virtue  of  its  own  weight  and  its  height  above  the 
ground,  and  the  kinetic  energy,  the  work  it  will  perform  in  falling  to 
the  ground,  is  the  product  of  those  two  quantities.  Similarly  in 
electricity,  the  energy  that  a  given  generator  will  transmit  is 
measured  by  the  product  of  the  current  it  is  capable  of  furnishing, 
multiplied  by  the  pressure  at  which  the  current  is  delivered  to  the 
cables  employed  in  transmitting  it.  Similarly,  it  appears  to  the 
author,  the  energy  involved  in  any  operation  where  heat  is  employed 
is  measured  by  the  two  quantities,  temperature  which  is,  as  explained, 
virtually  the  pressure,  and  entropy. 

Transmission  of  Heat 

It  is  usual  to  say  that  heat  is  transmitted  by  three  processes, 
radiation,  conduction,  and  convection.  To  the  author's  mind  the 


io       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

three  are  really  different  forms  of  the  same  thing — conduction, 
modified  by  the  conditions  under  which  the  heat  is  being  transmitted. 
Whenever  any  body  is  at  a  higher  temperature  than  surrounding 
bodies,  it  attempts  to  deliver  a  portion  of  its  heat  to  the  surrounding 
bodies,  and  will  continue  to  do  so  until  their  temperature  is  the  same 
as  its  own,  their  temperature  being  raised,  and  its  temperature  being 
lowered  in  the  process.  It  follows  that  a  heated  body  suspended,  say 
in  air,  sends  out  heat-waves  in  all  directions,  and  this  is  what  is 
known  as  radiation,  a  "  ray  "  which  wasjdealt  with  when  explaining 
refraction  and  reflection,  being  a  pencil  consisting  of  a  minute 
portion  of  a  succession  of  waves,  the  ray  extending  in  a  straight 
line  from  the  heated  body.  Conduction  is  known  as  the  process  by 
which  heat  is  conveyed  from  a  body,  or  a  portion  of  a  body,  at  a 
higher  temperature,  to  the  substances  immediately  in  contact  with  it. 
The  illustration  usually  given  is  that  of  a  poker  having  one  end  in  a 
fire.  The  end  in  the  fire  becomes  heated,  and  transmits  its  heat 
from  that  portion  in  the  fire  to  that  next  outside,  this  portion  trans- 
mitting its  heat  in  its  turn  to  the  portion  next  outside  of  it,  and  so 
on,  the  heat  travelling  through  the  length  of  the  poker,  and  if  time 
be  given,  the  outer  end  of  the  poker  becoming  very  hot,  the  heat  in 
this  case  being  transmitted  through  the  successive  portions  of  the 
poker  by  contact.  Conduction  also  takes  place  from  any  heated 
body,  such  as  a  steam-pipe,  or  the  outside  of  the  cylinder  of  a  steam- 
engine,  to  the  air  that  is  in  contact  with  it,  but  the  molecules  of  air 
being  free  to  move  among  themselves,  and  being  expanded  when 
heat  is  delivered  to  them,  tend  to  move  away  from  the  heated  surface, 
under  the  forces  of  expansion,  and  the  pressure  of  the  colder  mole- 
cules of  air  surrounding  them,  the  result  being  that  a  fresh  quantity 
of  air  reaches  the  heated  surface,  is  heated  and  expanded  in  its  turn, 
moves  away,  and  gives  place  to  another  body  of  air,  and  so  on. 
Practically  the  same  action  takes  place  with  water,  and  is  known 
as  convection.  It  is  the  method  by  which  heat  is  distributed  in 
rooms  and  places  where  the  air  is  in  motion,  and  in  boilers  and 
other  [vessels  where  water  or  other  liquids  are  being  heated.  It 
will  be  seen,  however,  that  the  process  of  convection  is  really  con- 
duction, with  the  subsequent  action,  caused  by  the  expansion  of  the 
gas  or  water  in  contact  with  the  heated  body. 

Air  and  gases  are  bad  conductors  of  heat ;  the  metals  are  all  good 
conductors ;  and  it  is  sometimes  said  that  air  is  transparent  to  what 
is  known  as  radiant  heat.  By  radiant  heat  the  author  understands 
the  heat-waves  which  pass  outwards,  or  radiate,  from  a  heated  body, 
and  as  he  understands  the  matter,  air,  nitrogen  and  oxygen  are 
apparently  transparent  to  the  heat-waves,  because  they  are  very 
deficient  in  another  property,  viz.  that  of  absorption  of  heat.  All 
substances  absorb  heat  when  heat-waves  are  delivered  to  them,  but 


INTRODUCTORY 


ii 


in  very  different  ratios,  and  the  gases  of  which  air  is  composed  have 
especially  low  absorbing  values.  According  to  the  late  Professor 
Tyndal,  carbonic  oxide  and  carbonic  acid  have  absorbing  values  at  the 
ordinary  atmospheric  pressure  ninety  times  as  great  as  that  of  either 
air,  oxygen,  or  nitrogen.  All  substances  vary  in  their  ability  to 
conduct  heat  in  the  sense  given  above,  as  illustrated  by  the  heated 
poker.  The  metals  are  the  best  conductors,  silver  being  the  best 
of  the  metals,  and  copper  standing  very  high.  The  following  table 
gives  the  relative  thermal  conductivities  of  different  metals. 


TABLE   II. 

TABLE  OF  RELATIVE  CONDUCTIVE  POWERS  OP  METAL  EMPLOYED  IN  STEAM 
APPARATUS,  SILVER  BEING  TAKEN  AS  THE  STANDARD. 


Silver. 
Copper 
Brass 


100-0  Zinc 

77-6  Tin 

33-0  Iron 


19-9  Steel    .          .     12-0 

14-5  Lead     .          .       8-5 

17-0  Platinum  8-2 


As  in  electricity,  the  substances  naturally  divide  into  thermal 
conductors  and  thermal  insulators,  the  former  being  employed  when 
it  is  required  to  transmit  heat  freely,  as  in  the  case  of  boiler-tubes 
and  boiler-flues,  where  conduction  is  required  from  the  hot  gases  to  the 
water ;  the  latter  being  employed  when  it  is  desired  to  prevent  the 
escape  of  heat,  as  in  the  substances  with  which  steam-pipes  and 
boilers  are  covered.  The  following  is  a  table  of  thermal  insulators. 
The  table  given  in  this  case  is  based  on  the  number  of  B.  Th.  units 
transmitted  per  square  foot  of  surface  per  hour  exposed,  with  the 
insulating  material  1  inch  in  thickness,  for  each  1°  F.  difference  of 
temperature. 


TABLE  III.  (LORENZ). 


Plaster  (ordinary)        .         .     2-67 
„       (very  fine)        .         .     4'2 

Brick          .         .         .      4-11-5-56 

Wood,  fir  (transmission  per- 
pendicular to  fibres)     '     .     0-75 

Wood,      fir      (transmission 
parallel  to  fibres)     .         .1-37 

Wood,  oak  (transmission  per- 
pendicular to  fibres) 

Cork 

Indiarubber 

Gutta  percha 


Glass 


1-70 
.     1-15 
.     1-37 
.     1-39 
6-05-7-10 


Quartz  sand  in  powder 
Brick  dust. 
Chalk  in  powder 
Wood  ashes 
Sawdust,  mahogany 
Charcoal  powdered 
Coke  powdered. 
New  calico 
Cotton  or  sheep's  wool 
Eider  down 
Mineral  wool  . 
Hair  felt  . 


.     2-18 
1-12-1-33 
0-694-0-870 
0-484 
0-524 
0-637 
1-29 
0-403 
0-323 
0-315 
0-38-0-47 
0-40 


Thermal  conductivity  is  defined  by  scientists  as  the  ratio  of  rate 
of  transmission  of  heat,  through  the  substance  in  question,  to  the 
temperature  gradient.  The  rate  of  transmission  is  proportional  to 
the  temperature  gradient,  and  is  the  quantity  of  heat  transmitted  in 
unit  time,  through  unit  area  of  cross  section  of  the  substance,  the 


12       STEAM   BOILERS,   ENGINES,   AND    TURBINES 

unit  cross  section  being  perpendicular  to  the  lines  of  flow  of  the  heat. 
By  the  temperature  gradient  is  meant  the  gradual  fall  of  tempera- 
ture between  the  two  surfaces,  one  of  which  is  at  a  higher  tempera- 
ture than  the  other.  The  following  formula  is  given  for  the  rate  of 
transmission  of  heat : — 

Bate  of  transmission  -^  =  Jc(S'  -  0")x 

where  Q  is  the  quantity  of  heat  transmitted  through  the  sectional 
area  A  in  time  T,  and  k  is  the  conductivity,  x  the  thickness  of  the 
substance,  and  '0'  —  0"  the  temperature  gradient.  For  practical  pur- 
poses the  rate  of  transmission  of  heat  between  any  two  surfaces  may 
be  taken  to  be  proportional  to  the  difference  of  temperature  between 
the  two  surfaces,  to  the  area  of  the  surfaces,  and  to  the  thermal  con- 
ductivity of  the  substances  interposed  between  them,  or  inversely  to 
the  thermal  resistance  of  the  interposed  substance. 

Thermal  Conductivity  of  Finely  Divided 
Substances 

It  had  better  be  noted  here  that  the  thermal  conductivity  of  any 
substance,  in  a  finely  divided  state,  is  very  low.  The  reason  is,  as 
the  author  understands  the  matter,  when  the  substance  is  in  a  finely 
divided  state,  as  in  a  fine  powder  with  its  particles  loosely  in  con- 
tact with  each  other,  there  are  a  very  large  number  of  minute  air 
spaces  between  the  particles,  and  the  heat  current,  in  passing  through 
the  substance,  has  to  pass  across  these  minute  air  passages,  which 
offer  a  very  high  thermal  resistance,  providing  that  moisture  is  not 
present.  Dry  air,  when  absolutely  motionless,  is  one  of  the  best 
thermal  insulators.  It  offers  a  very  high  thermal  resistance.  In 
addition  to  this,  the  resistance  offered  by  a  loose  agglomeration  of 
minute  bodies  to  the  passage  of  heat  or  electricity  is  always  high, 
because  there  is  always  a  resistance  set  up  when  any  physical  force 
passes  from  one  substance  to  another.  In  electricity,  what  is  known 
as  contact  resistance  is  always  high,  and  the  same  thing  rules  in  the 
transmission  of  heat. 

The  above  is  of  particular  importance  in  connection  with  steam- 
boilers  and  their  accessories,  because  the  finely  divided  particles  of 
carbon,  which  are  built  up  on  the  surfaces  of  flues,  or  on  the  surfaces 
of  the  tubes  of  water-tube  boilers,  and  of  economizers,  and  on  the 
inside  of  chimneys,  reduce  the  efficiencies  of  those  apparatus.  On 
the  other  hand,  the  property  mentioned  is  of  great  value,  where  it 
can  be  applied,  to  prevent  the  egress  of  heat,  say  from  steam-pipes, 
the  surfaces  of  steam-boilers,  etc.  Many  of  the  substances  that  are 
sold  for  insulating  steam-pipes  and  steam-boilers,  such  as  silicate 


INTRODUCTORY 


cotton,  finely  divided  charcoal,  and  others,  owe  their  thermal  insu- 
lating value  to  these  properties.  The  property  occurs  in  another 
form,  but  with  equal  value,  where  it  can  be  employed,  in  cork. 
Cork  is  built  up  of  a  number  of  very  minute  air  cells,  each  enclosed 
in  a  fine  membrane,  and  any  heat  passing  through  a  mass  of  cork 
has  to  pass  through  the  air-cells,  and,  as  mentioned  above,  to  pass 
in  succession  from  the  menibrane  to  the  air,  from  the  air  to  the  mem- 
brane again,  and  so  on. 

Specific  Heat 

Specific  heat  is  the  ratio  between  the  quantity  of  heat  required  to 
raise  the  temperature  of  1  Ib.  of  any  substance  1°  F.,  compared  with 
that  required  to  raise  the  temperature  of  1  Ib.  of  water  at  39°  F.  to 
40°  F.,  39°  F.  being  the  greatest  density  of  water. 

The  British  Thermal  Unit. — The  specific  heat  of  water  is  taken 
as  1,  and  what  is  known  as  the  heat  unit,  or  the  B.  Th.  unit,  is  the 
quantity  of  heat  required  to  raise  the  temperature  of  1  Ib.  of  water 
from  39°  F.  to  40°  F.  The  table  gives  a  list  of  the  specific  heats  of  a 
number  of  substances. 

TABLE  IV. 
SPECIFIC  HEATS  OF  VAEIOUS  SUBSTANCES  (STIRLING  BOILER  Co.). 

Solids. 


Copper 
Gold  . 

Wrought  iron 
Cast  iron    . 
Steel  (soft) . 
„     (hard) 
Zinc  . 
Brass . 
Glass . 
Lead  . 
Platinum    . 
Silver 
Tin     . 
Ice 

Sulphur 
Charcoal 


Water 
Alcohol 
Mercury 
Benzine 
Glycerine 
Lead  (melted) 
Sulphur  (melted 
Tin  (melted) 
Sulphuric  acid 
Oil  of  turpentine 


Liquids. 


0-0951 
0-0324 
0-1138 
0-1298 
0-1165 
0-1175 
0-0956 
0-0939 
0-1937 
0-0314 
0-0324 
0-0570 
0-0562 
0-5040 
0-2026 
0-2410 


1-0000 
0-7000 
0-0333 
0-4500 
0-5550 
0-0402 
0-2340 
0-0637 
0-3350 
0-4260 


STEAM   BOILERS,   ENGINES,   AND   TURBINES 


At  constant 

At  constant 

pressure. 

volume. 

0-2375 

0-1685 

0-2175 

0-1551 

0-2438 

0-1727 

3-4090 

2-4123 

0-4805 

0-346 

0-2479 

0-1758 

0-2170 

0-1535 

0-4040 

0-173 

0-2277 

0-240 

Gases. 


Air  (at  freezing-point) 
Oxygen    . 
Nitrogen  . 
Hydrogen 

Superheated  steam  * 
Carbon  monoxide  (CO) 

„       dioxide  (C02) 
Olefiant  gas 
Blast-furnace  gas 
Chimney  gases  (approx. 

The  absolute  unit  of  heat  is  the  calorie.  It  is  the  unit  based 
upon  the  centimeter-gramme-second  system  of  units,  and  is  the 
quantity  of  heat  required  to  raise  the  temperature  of  1  gramme  of 
water  from  4°  C.  to  5°  C.,  and  is  equal  to  0-00396  British  Thermal 
Units.  The  British  Thermal  Unit  is  usually  written  B.  Th.  U. 

In  France  and  on  the  Continent,  where  the  centimeter-gramme- 
second  system  is  employed,  another  unit,  the  great  calorie,  is  used. 
This  is  the  quantity  of  heat  required  to  raise  1  kilogramme  (1000 
grammes)  =  2*2  Ibs.  of  water  from  4°  C.  to  5°  C.  The  great  calorie 
is  =-.  3-968  B.  Th.  units. 

The  specific  heat  of  most  substances  varies  with  the  temperature, 
that  of  water  increasing  with  the  temperature ;  the  specific  heat  of 
water  increases  from  1*0  at  the  point  of  greatest  density,  to  1-013  at 
212°  F.,  and  to  1-0364  at  356°  F.,  and  1-0568  at  446°  F.  But  for  all 
practical  purposes  the  specific  heat  of  water  is  taken  as  unity, 
throughout  the  range  of  temperature  employed  in  boiler  work.  The 
following  table  gives  the  specific  heats  of  the  principal  substances 
employed  in  connection  with  steam : — 


TABLE  V. 


Aluminium                     0-2181 

Coal  (bituminous)          0-2777 

Antimony 

0-0508 

„     (anthracite) 

0-2017 

Brass 

0-0939 

Glass 

0-1977 

Copper     . 

0-0951 

Olive  oil  . 

0-3096 

Iron  (cast) 

0-1298 

Air. 

0-2669 

„     (wrought) 

0-1138 

Oxygen    . 

0-2361 

Lead 

0-0314 

Hydrogen 

3-2936 

Nickel     . 

0-1086 

Nitrogen  . 

0-2754 

Steel 

0-1165 

Carbonic  acid 

0-2210 

Tin. 

0-0562 

,,        oxide 

0-2884 

Zinc 

0-0955 

Wood  (oak) 

0-570 

Brickwork 

0-20 

»      (fir) 

0-650 

Limestone                     0-2174 

The  specific  heat  of  superheated  steam  is  variable. 


INTRODUCTORY  15 

The  Mechanical  Equivalent  of  Heat 

The  first  law  of  thermodynamics  states  that  heat  and  mechanical 
work  are  interchangeable,  and  the  classical  experiments  of  Joule, 
confirmed  later  by  numerous  other  experimenters,  has  shown  that 
the  B.  Th.  unit  has  a  definite  mechanical  equivalent.  That  is  to 
say,  the  energy  present  in,  or  delivered  by,  1  B.  Th.  unit,  has  its 
definite  equivalent  in  mechanical  energy.  Joule  made  the  equivalent 
772  foot  Ibs.,  but  later  experimenters — Eowland  of  Baltimore  in 
particular — have  made  it  778  foot  Ibs.,  and  the  latter  figure  is  that 
which  is  taken  for  calculation  at  the  present  time.  The  meaning  of 
the  mechanical  equivalent  of  heat  is,  that  when  heat  is  delivered  to 
water,  in  the  process  of  converting  it  into  steam,  or  is  delivered  to 
steam  to  raise  it  to  a  higher  temperature,  the  ability  is  conferred 
upon  the  steam  of  performing  mechanical  work,  just  as  the  ability  is 
conferred  upon  a  weight  of  performing  work,  by  raising  it  above  the 
surface  of  the  earth,  and  the  work  done  by  steam  in  cooling,  is 
directly  proportional  to  the  heat  it  loses  in  the  process,  as  measured 
by  the  mechanical  equivalent. 

The  Rate  of  doing  Work 

The  unit  of  mechanical  work  is  the  foot  lb.,  the  work  that  1  Ib. 
will  perform  in  falling  to  earth  from  a  height  of  1  foot,  or  any 
equivalent  of  this,  such  as  the  work  that  2  Ibs.  will  perform  in  falling 
from  a  height  of  6  inches,  £  lb.  in  falling  from  a  height  of  2  ft.,  and 
so  on.  When  work  is  performed  at  the  rate  of  33,000  foot  Ibs.  per 
minute,  or  550  foot  Ibs.  per  second,  it  is  said  to  be  at  the  rate  of 
1  H.P.,  that  is  to  say,  the  engine  that  is  able  to  do  work  at  this  rate 
is  supposed  to  be  working  at  the  rate  at  which  a  horse  would  work, 
in  drawing  a  load,  or  in  any  other  way.  The  33,000  foot  Ibs.,  or  the 
550  foot  Ibs.  may  be  in  any  form  in  which  the  two  factors,  the  weight 
and  the  distance  through  which  it  falls,  will  make  up  these  figures 
when  multiplied  together.  Thus  a  weight  of  55  Ibs.  falling  through 
a  vertical  distance  of  10  ft.  in  1  second,  performs  work  at  the  rate  of 
I  H.P.,  and  similarly  5.]  Ibs.  falling  through  100  ft.  performs  work  at 
the  same  rate. 

The  B.  Th.  unit,  it  will  be  seen,  is  directly  connected  with  the 
H.P.  from  the  fact  that  it  requires  the  expenditure  of  33,000  ~-  778 
=  42 '4  B.  Th.  units  per  minute  to  perform  work  at  the  rate  of  1  H.P., 
on  the  supposition  that  the  whole  of  the  energy  of  the  heat  is 
converted  into  useful  mechanical  work.  As  will  be  seen  later  in  the 
book,  the  whole  of  the  heat  energy  delivered  to  the  steam  is  never 
converted  into  useful  mechanical  work.  There  are  several  charges 
for  conversion,  etc.,  on  the  way. 


16       STEAM   BOILERS,   ENGINES,   AND   TURBINES 


Expansion  of  Bodies  in  the  Presence  of  Heat 

Nearly  all  substances  expand  with  increased  temperature,  in  a 
certain  definite  ratio,  with  each  degree  of  increase.  The  ratio  is 
known  as  the  coefficient  of  expansion.  The  coefficients  of  expansion 
of  different  substances  are  given  in  the  following  table  : — 


Aluminium 
Brass 
Copper    . 
Iron  (cast) 

,,     (wrought) 
Steel 
Lead       . 
Platinum 
Tin 
Zinc 

Cement  . 
Concrete. 
Glass 
Granite  . 
Brickwork 
Porcelain 
Slate 

Sandstone 
Wood  (pine)     . 


TABLE  VI. 

Expansion  per  1°  F. 
0-00001234 

0-00000957  to  0-00001052 
0-00000887 
0-00000556 

0-00000626  to  0-00000648 
0-00000636  to  0-00000689 
0-00001571 
0-00000479 
0-00001163 
0-00001407 

0-00000594  to  0-00000797 
0-00000795 

0.00000397  to  0-00000499 
0-00000438  to  0-00000498 
0-00000256  to  0-00000494 
0-00000200 
0-00000577 

0-00000494  to  0-00000652 
0-00000276 


Expansion  per  1°  C. 
0-00002221 

0-00001722  to  0-00001894 
0-00001596 
0-00001001 

0-00001126  to  0-00001166 
0-00001144  to  0-00001240 
0-00002828 
0-00000863 
0-00002094 
0-00002532 

0-00001070  to  0-00001435 
0-00001430 

0-00000714  to  0-00000897 
0-00000789  to  0-00000897 
0-00000460  to  0-00000890 
0-00000360 
0-00001038 

0-00000750  to  0-00001174 
0-00000496 


Water  also  expands  from  the  point  of  greatest  density  to  the 
freezing-point,  and  also  with  increasing  temperature,  the  relative 
volumes  being  at  212°  F.  1'0466,  at  300°  1-09563,  at  400°  1-15056, 
and  at  500°  1*2205,  the  volume  at  the  point  of  greatest  density  being 
taken  as  unity.  All  liquids  expand  in  different  ratios. 

Nearly  all  substances  also  contract  on  cooling,  and  this  is  the 
property  that  enables  metals  to  be  cast  in  different  patterns.  A  few 
substances,  such  as  bismuth,  expand  on  cooling,  and  these  are  available 
for  certain  work.  Water  expands  when  frozen.  One  important  point 
in  connection  with  the  expansion  of  different  substances,  is  the  relative 
rates  at  which  different  substances  expand  with  the  same  increase 
of  temperature.  Where  two  metals,  for  instance,  are  employed 
together  in  a  piece  of  machinery,  and  are  exposed  to  heat,  if  they 
expand  at  different  rates,  the  result  may  sometimes  be  serious  ;  cracks, 
for  instance,  being  formed  in  vessels  containing  hot  substances,  or 
explosive  gases,  leaks  being  caused  in  valves,  etc. 

Latent  Heat 

A  great  many  substances,  experiment  does  not  enable  us  to  say 
whether  all  substances,  may  exist  in  one  of  three  states — the  solid,  the 


INTRODUCTORY  17 

liquid,  or  the  gaseous.  In  the  solid  state  the  molecules  of  the  sub- 
stance are  very  close  together,  and  are  not  easily  moved  upon  each 
other,  force  being  required  to  separate  them,  the  force  varying  with 
the  substance ;  metals,  and  particularly  iron  and  steel,  requiring  the 
largest  expenditure  of  force  to  rend  them.  In  the  liquid  state  the 
molecules  are  also  close  together,  though  not  as  close  as  in  the  solid 
state,  but  they  are  able  to  move  freely  over  each  other,  and  require 
the  expenditure  of  very  little  force  to  cause  them  to  do  so.  In  the 
gaseous  state  the  molecules,  according  to  the  latest  modern  views,  are 
very  much  more  widely  separated  than  in  either  the  liquid  or  the 
solid  state,  and  they  are  in  constant  motion.  Gases  and  liquids  are 
both  called  "  fluids  "  in  scientific  language,  many  properties  being 
common  to  both  of  them.  The  main  difference  between  the  solid,  the 
liquid,  and  the  gaseous  state  is  the  presence  or  absence  of  a  certain 
quantity  of  heat.  With  a  great  many  substances,  if  heat  be  applied 
to  a  body  of  the  substance  in  the  solid  condition,  its  temperature  will 
rise,  and  in  many  cases  it  will  soften,  as  the  heat  is  delivered  to  it ; 
but  at  a  certain  temperature  it  will  commence  to  pass  into  the  liquid 
condition,  the  temperature  remaining  constant,  till  the  whole  of  the 
substance  to  which  the  heat  is  being  delivered,  has  become  liquid.  If 
heat  is  still  applied,  the  temperature  of  the  liquid  will  again  increase, 
the  liquid  expanding,  as  explained  in  a  previous  paragraph,  until  at 
another  certain  temperature  the  liquid  will  commence  to  pass  into 
the  gaseous  condition,  the  temperature  again  remaining  constant 
until  all  the  liquid  has  become  gas.  The  most  striking  instance  of 
this,  and  the  one  that  is  of  most  importance  in  connection  with  steam, 
is  that  of  water.  Water  exists  in  the  solid  state  as  ice,  in  the  liquid 
state  as  water,  and  may  be  made  to  exist  in  the  gaseous  state  as  steam. 
In  the  neighbourhood  of  the  poles,  it  exists  principally  as  ice.  In 
the  tropics  and  in  the  temperate  zones,  it  exists  principally  as  water, 
but  it  may  be  made  to  exist  as  steam,  and  it  exists  largely  as  vapour 
in  all  latitudes.  If  a  block  of  ice  weighing  say  1  Ib.  be  heated,  it 
will  be  found  that  the  temperature  of  the  ice,  which  is  usually  below 
freezing-point  if  the  ice  is  stable,  will  gradually  rise  to  32°  F.  or  0°  C., 
and  at  that  point  the  ice  will  begin  to  form  water,  and  if  a  thermo- 
meter be  placed  in  the  melting  mass,  it  should  remain  constant,  at 
freezing-point,  until  the  whole  of  the  ice  has  become  water.  If  a 
measurement  of  the  quantity  of  heat  delivered  to  the  melting  ice  be 
taken,  it  will  be  found  to  be  exactly  142*4  B.  Th.  units  for  1  Ib.  of 
pure  water  ice  melting  to  water.  If  heat  is  applied  to  the  water,  its 
temperature  will  rise  steadily,  until  at  212°  F.  or  100°  C.,  at  standard 
barometric  pressures  and  at  sea-level,  the  water  will  commence  to  pass 
into  the  form  of  steam,  and  the  temperature  again  will  remain  at 
212°  F.,  until  all  the  water  has  become  steam.  If  the  quantity  of 
heat  again  be  measured,  it  will  be  found  that  966  B.  Th.  units  have 

c 


1 8      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

been  absorbed  in  converting  the  1  Ib.  of  water  at  212°  into  1  Ib.  of 
steam.  The  heat  required  to  convert  1  Ib.  of  water  into  steam 
is  called  the  latent  heat  of  steam,  and  the  quantity  of  heat  required  to 
convert  1  Ib.  of  ice  at  32°  F.  into  water,  is  the  latent  heat  of  water, 
though  the  expression  is  not  often  used. 


The  Variation  of  the  Boiling=point 

The  boiling-point  of  every  liquid,  the  temperature  at  which  it  will 
commence  to  pass  from  the  liquid  to  the  gaseous  condition,  varies 
with  the  pressure  to  which  the  surface  of  the  liquid  is  exposed.  For 
standard  calculations,  the  standard  atmospheric  pressure  is  taken, 
this  being  760  mm.  or  29'962  inches  at  sea-level.  Our  earth,  it 
will  be  remembered,  is  surrounded  by  an  envelope  of  what  we  call 
atmospheric  air,  extending  from  the  surface  to  a  considerable 
height. 

The  atmosphere  contains  what  we  call  air,  consisting  principally 
of  the  two  gases,  oxygen  and  hydrogen,  and  it  also  contains  quantities 
of  the  vapour  of  water — as  will  be  described  more  fully  in  dealing  with 
air — and  other  substances,  such  as  dust  that  rises  from  the  earth, 
meteoric  dust,  the  vapours  of  different  substances  that  arise  from  the 
earth,  particularly  in  manufacturing  districts.  The  air  and  the  other 
substances  all  have  weight ;  a  cubic  foot  of  air  at  the  standard 
atmospheric  pressure,  and  at  32°  F.,  weighs  O08  of  a  Ib. 

The  average  weight  of  the  column  of  air  supported  upon  a 
surface  of  the  earth  1  square  inch  in  area  is  taken  to  be 
147  Ibs.  The  weight  of  the  column  of  air  above  the  earth's  sur- 
face is  known  as  the  atmospheric  pressure;  14*7  Ibs.  per  square 
inch,  is  referred  to  as  a  pressure  of  one  atmosphere.  The  atmo- 
spheric pressure  is  usually  measured  by  the  column  of  mercury  that 
it  will  support,  in  the  ordinary  vertical  mercurial  barometer.  The 
ordinary  vertical  mercurial  barometer,  which  is  familiar  to  every 
one,  consists  of  a  vertical  tube,  closed  at  the  top,  in  which  a  quantity 
of  mercury  is  placed,  the  lower  end  of  the  tube  dipping  into  a  vessel 
also  containing  mercury,  and  open  to  the  atmosphere.  The  pressure 
of  the  atmosphere  upon  the  mercury  in  the  open  vessel  forces  that  in 
the  tube  upwards,  and  the  height  of  the  mercury  in  the  barometric 
tube  indicates  from  hour  to  hour  the  variation  in  the  pressure  of  the 
atmosphere  or  in  its  weight.  A  glance  at  any  barometric  chart,  such 
as  those  that  are  printed  in  the  columns  of  the  Times  and  other 
papers,  will  show  that  at  any  particular  place  the  barometric  pressure 
varies  from  day  to  day,  often  by  large  amounts  on  successive  days, 
and  even  within  a  few  hours.  It  also  varies  from  place  to  place,  this 


INTRODUCTORY  19 

variation  being  one  cause  of  the  winds  which  blow  over  different 
countries.     The  variation  in  the  pressure  of  the  atmosphere  at  any 
point  on  the  surface  is  due  to  the  variation  in  the  weight  of  the 
atmosphere  above  that  point,  this  being  due  again  largely  to  the 
variation  in  the  quantity  of  the  vapour  of  the  water  present  there. 
Every  one  is  familiar  with  the  saying,  that  when  the  glass — the 
barometer — is  going  down  we  shall  probably  have  rain,  and  vice  versa. 
When  the  indications  of  the  barometer  are  low,  it  is  due  to  the  weight 
of  the  atmosphere  at  the  point  where  the  barometer  is  fixed  being  less 
than  the  normal,  this  again  being  due  to  the  displacement  of  a  certain 
portion  of  the  air  above  by  a  certain  quantity  of  the  vapour  of  water, 
the  vapour  of  water  weighing  considerably  less  than  the  air  it  displaces. 
Air  and  whatever  it  holds  in  suspension,  being  fluid,  has  one  of  the 
important   properties    of   all   fluids,   it   transmits   pressures   in   all 
directions,  wherever  it  is  present.     Thus  we  are  all  familiar  with  the 
fact  that  though  we  are  subject  to  the  average  pressure  of  14*7  Ibs. 
per  square  inch,  at  every  part  of  our  bodies,  and  even  of  parts  of  our 
internal  organisms,  such  as  our  lungs,  and  that  if  the  total  pressure 
on  our  bodies  was  summed  up  it  would  be  somewhat  considerable ; 
yet  we  are  absolutely  unconscious  of  the  fact,  because,  owing  to  the 
equal  transmission  of  pressure  everywhere,  by  the  fluid  air  and  what- 
ever it  may  have  absorbed  the  pressure  is  equal  everywhere.     Hence, 
in  any  vessel  in  which  water  is  contained,  for  the  purpose  of  being 
boiled,  the  pressure  of  the  air,  whatever  it  may  be  at  the  moment,  is 
present  at  every  part  of  the  surface  of  the  water,  and  in  order  that  the 
water  may  boil,  that  is  that  it  may  throw  out  gas  into  the  atmosphere, 
it  must  become  possessed  of  sufficient  energy,  or  rather  must  deliver 
sufficient  pressure  to  the  vapour  it  is  throwing  off,  to  overcome  the 
pressure  of  the  atmosphere.     The  operation  of  boiling,  in  fact,  in  the 
case  of  any  liquid,  consists  of  the  formation  of  a  gas,  and  the  delivery 
to  that  gas  at  a  pressure  sufficient  to  enable  it  to  escape  into  the 
atmosphere,  notwithstanding  the  pressure  exerted  by  the  atmosphere 
upon  the  surface  of  the  liquid  from  which  the  gas  is  escaping.     The 
matter  may  be  put  in  another  way.     All  liquids  evaporate  at  all 
temperatures,  and  this  is  particularly  true  of  water.     The  vapour 
which  is  coming  away  from  the  surface  of  the  liquid,  exerts  a  certain 
pressure  upon  the  atmosphere  into  which  it  is  escaping,  and  when 
this  pressure  is  equal  to  that  of  the  atmosphere,  the  liquid  becomes  a 
gas  very  freely,  and  is  said  to  boil.     It  will  easily  be  understood  from 
the  above,  that  an  increase  or  decrease  of  pressure  on  the  surface  of 
the  liquid  changes  the  temperature  at  which  boiling  takes  place.     It 
is  a  well  known  fact  that  water  boils  at  a  lower  temperature  on 
mountain  tops,   owing  to   the  lower  pressure   of    the   atmosphere 
there. 

The  standard  boiling-point  of  water  is  taken  as  212°  at  sea-level, 


20      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

with  the  barometer  constant  at  29*962.  At  the  first  floor  of  the 
Paris  Observatory,  which  is  213  feet  above  sea-level,  the  standard 
barometric  pressure  is  29*69,  and  the  boiling-point  of  water  211*5° 
F.  At  Moscow,  at  a  height  of  984  feet  above  sea-level,  the  standard 
barometric  pressure  is  28*82,  and  the  boiling-point  of  water  210'2°.  At 
Madrid,  which  is  1995  feet  above  sea-level,  the  standard  barometric 
pressure  is  27*72,  and  the  boiling-point  of  water  208°.  At  the  Hospice 
of  St.  Gothard,  6808  feet  above  sea-level,  the  standard  barometric 
pressure  is  23*07,  boiling-point  of  water  199*2°.  At  Quito,  in  Peru, 
9541  feet  above  sea-level,  standard  barometric  pressure  is  20*75,  boiling- 
point  of  water  194*2°.  Table  VII.  gives  the  boiling-points  at  different 


TABLE   VII. 
BOILING-POINT  OF  WATER  AT  VARIOUS  ALTITUDES. 


Boiling-point 
in  degrees. 
Fahrenheit. 

Altitude  above 
sea-level.   Feet. 

Atmospheric  pres-           Barometer, 
sure.     Pounds  per             $rnchees 
square  inch. 

184 

15,221 

8-19    '                16-79 

185 

14,649 

8-37                     17-16 

186 

14,075 

8-56                     17-54 

187 

13,498 

8-75                     17-93 

188 

12,934 

8-94                     18-32 

189 

12,367 

9-13                     18-72 

190 

11,799 

9-33                     19-13 

191 

11,243 

9-53                     19-54 

192 

10,685 

9-74                     19-96 

193 

10,127 

9-95                     20-39 

194 

9,579 

10-16 

20-82 

195 

9,031 

10-38 

21-26 

196 

8,481 

10-60 

21-71 

197 

7,932 

10-82 

22-17 

198 

7,381 

11-05 

22-64 

199 

6,843 

11-28 

23-11 

200 

6,304 

11-52 

23-59 

201 

5,764 

11-76 

24-08 

202 

5,225 

12-01 

24-58 

203 

4,697 

12-25 

25-08 

204 

4,169 

12-51 

25-59 

205 

3,642 

12-77 

26-11 

206 

3,115 

13-03 

26-64* 

207 

2,589 

13-29 

27-18 

208 

2,063 

13-57 

27-73 

209 

1,539 

13-84 

28-29 

210 

1,025 

14-12 

28-85 

2111- 

512 

14-41 

29-42 

212 

Sea-level. 

14-70 

30-00 

i 

heights  above  sea-level.     It  may  be  noted  incidentally  that  mountain 
sickness  is  largely  due  to  the  decreased  atmospheric  pressure ;  the 


INTRODUCTORY  21 

lungs  and  the  stomach,  which,  it  will  be  remembered,  work  together 
in  the  process  of  respiration,  requiring  some  time  to  accommodate 
themselves  to  the  lowered  pressure  at  considerable  heights. 

On  the  other  hand,  an  increased  pressure  raises  the  boiling 
temperature.  From  the  table  of  properties  of  saturated  steam  that 
is  given  on  p.  24,  it  will  be  seen  that  while  the  boiling-point  with 
147  Ibs.  pressure  is  212°  F.,  with  50  Ibs.  pressure  it  is  281°,  with 
80  Ibs.  pressure  it  is  312°,  with  120  Ibs.  pressure  it  is  341°,  and 
with  200  Ibs.  pressure  382°,  while  with  lower  pressures,  such  as  are 
obtained  when  engines  are  working  on  a  condenser  with  10  Ibs. 
pressure,  the  boiling-point  is  193°,  with  5  Ibs.  it  is  162°,  and  with 
1  Ib.  it  is  102°. 


The  Influence  of  Dissolved  Substances  upon  the 
Boiling-point  of  Water. 

Water,  as  is  explained  later,  dissolves  a  very  large  number  of 
substances,  liquid,  solid,  and  gaseous,  and  the  act  of  solution  changes 
the  temperature  of  the  boiling-points  and  of  the  freezing-points. 
Brine  made  with  a  solution  of  common  salt,  and  of  calcium  chloride, 
is  used  with  refrigerating  apparatus,  because  it  does  not  freeze  at 
ordinary  temperatures,  and  can  be  kept  in  circulation  at  practically 
any  low  temperature  that  may  be  desired,  for  cold  stores,  or  for  ice- 
making  plant.  On  the  other  hand,  the  presence  of  salts  in  solution 
raises  the  boiling  temperature.  The  increase  has  been  measured 
for  a  large  number  of  substances.  Common  salt  is  one  of  the 
substances  of  which  the  largest  number  of  measurements  have  been 
taken,  as  it  is,  or  it  would  be  more  correct  to  say  was,  so  commonly 
employed  in  the  boilers  of  steam  ships.  Three  per  cent,  of  salt  raises 
the  boiling  point  to  213'2°  F.,  at  standard  atmospheric  pressure; 
6  per  cent,  raises  it  to  214'4°  F. ;  9  per  cent,  to  215'5°  F. ;  12  per 
cent,  to  216*7°  F. ;  and  approximately  it  may  be  taken  that  each 
3  per  cent,  of  salt  increases  the  boiling-point  1°  F.  Other  substances, 
such  as  chloride  of  calcium,  nitrate  of  soda,  nitrate  of  ammonia, 
carbonate  of  soda,  chloride  of  potassium,  also  raise  the  boiling-point 
in  various  proportions. 

It  should  be  noted  that  while  the  boiling-point  of  the  solution 
is  raised,  the  steam  which  is  formed  from  the  solution  is  of  pure 
water,  though  it  may  contain  minute  portions  of  the  salt,  held  in 
mechanical  suspension.  Bodies  held  in  mechanical  suspension  in 
water,  do  not  affect  its  boiling-point.  Thus  the  finely  divided 
substances  that  are  taken  up  by  water  in  its  course  over  rocks,  etc., 


22       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

have  no  effect  upon  the  temperature  at  which  the  water  holding  it 
will  boil. 


Absolute  Pressure 

The  pressures  given  in  the  last  paragraph  are  termed  "  absolute 
pressures,"  the  pressure  above  zero.  In  the  ordinary  steam  working, 
the  steam  gauge  indicates  pressure  above  the  atmosphere,  and  in 
order  to  obtain  figures  for  absolute  pressure,  it  is  necessary  to  add 
to  the  gauge  pressure  14*7  Ibs.  Absolute  pressures  are  usually 
employed  in  calculations,  and  the  two  pressures  are  distinguished, 
when  talking  or  writing,  by  the  names  "absolute"  and  "gauge" 
pressures. 


Variation  of  the  Latent  Heat  with  Variation 
of  Pressure 

It  has  been  explained  above  that  the  boiling-point  varies  with 
the  pressure.  It  will  be  understood  that  immediately  steam  com- 
mences to  be  formed,  in  a  closed  vessel,  such  as  a  boiler,  the  pressure 
increases,  and  with  it  the  temperature  at  which  the  water  will  form 
steam.  In  practice  steam  is  allowed  to  continue  to  be  formed,  until 
the  pressure  reaches  that  with  which  the  engines,  turbines,  etc.,  are 
working,  and  in  good  practice  it  is  maintained  approximately  at  this 
pressure,  so  long  as  the  plant  is  working.  Any  increase  of  pressure 
however  caused,  say,  by  engines  not  taking  steam  for  a  time,  increases 
the  temperature  at  which  the  steam  will  be  formed,  and  vice  versa. 
It  will  be  understood,  of  course,  that  in  any  boiler  in  which  steam 
is  being  formed,  the  temperature  of  the  water  and  of  the  steam  being 
formed  from  it,  are  the  same,  or  at  least  that  portion  of  the  water 
that  is  directly  in  contact  with  the  steam,  and  from  which  the  steam 
is  issuing.  In  addition  to  the  temperature  at  which  steam  is  formed 
increasing  and  decreasing  with  the  rise  and  fall  of  pressure,  the 
latent  heat  also  changes,  but  inversely.  As  the  pressure  rises,  the 
temperature  rises,  and  the  latent  heat  falls,  and  vice  versa.  The  matter 
may  be  looked  upon  in  the  following  manner.  Taking  water  at 
average  temperature,  say  60°,  a  certain  quantity  of  heat  is  required  to 
raise  it  to  boiling-point.  With  standard  pressure,  14*7  Ibs.  per  square 
inch,  152  B.  Th.  units  are  required  to  raise  every  pound  of  water  to 
boiling  temperature,  and  966  units  are  required  to  convert  the  pound 
of  water  into  steam  at  the  same  temperature.  With  a  pressure  of 
50  Ibs.  per  square  inch  absolute,  the  boiling  temperature  being 


INTRODUCTORY  23 

281°  F.,  221  B.  Th.  units  are  required  to  raise  the  water  to  boiling 
temperature,  but  only  916*3  units  are  required  to  convert  it  into 
steam  at  that  temperature,  and  so  on  with  higher  pressures.  On  the 
other  hand,  with  lower  pressures,  such  as  are  obtained  by  condensa- 
tion of  the  exhaust  steam  from  engines  and  turbines,  the  latent  heat 
of  the  steam,  the  quantity  of  heat  retained  by  the  steam,  as  long  as 
it  remains  steam,  steadily  increases.  At  10  Ibs.  absolute  pressure 
the  latent  heat  has  risen  to  978*4  B.  Th.  units,  at  5  Ibs.  absolute 
pressure  it  has  risen  to  1000*3  units,  and  at  1  Ib.  absolute  pressure  it 
is  1042 '9  units.  It  will  be  seen  that  this  is  an  important  matter, 
when  dealing  with  the  work  that  is  to  be  obtained  from  steam 
engines  and  steam  turbines,  because  the  useful  work  obtainable 
depends  entirely  upon  the  number  of  heat  units  that  can  be  abstracted 
from  the  steam  in  the  course  of  the  performance  of  mechanical  work. 
It  should  be  noted,  however,  that  the  total  quantity  of  heat  required 
by  each  pound  of  water  to  raise  it  to  boiling-point,  and  to  convert  it 
into  steam  at  different  pressures,  •  steadily  increases  as  the  pressure 
increases.  Taking  water  at  60°,  with  an  absolute  pressure  of  1  Ib. 
per  square  inch,  1084  heat  units  are  required  to  bring  it  to  boiling-point 
and  to  convert  it  into  steam.  At  10  Ibs.  absolute  pressure  the 
quantity  has  risen  to  1112  units.  At  standard  atmospheric  pressure 
14*7  Ibs.  per  square  inch,  it  has  risen  to  1118  units.  At  50  Ibs.  absolute 
it  is  1139  units.  At  100  Ibs.  absolute  it  is  1153  units;  and  at 
200  Ibs.  absolute  it  is  1170.  It  goes  on  increasing  with  higher 
temperatures  and  higher  pressures  up  to  approximately  466  Ibs.  per 
square  inch  absolute,  when  the  boiling  temperature  is  460°  F.,  the  latent 
heat  being  777*4  B.  Th.  units,  and  the  total  heat  delivered  to  the 
water  to  raise  its  temperature  and  to  convert  it  into  steam  from 
60°  is  1186,  according  to  the  experiments  of  Dr.  de  Laval.  The 
latent  heat  of  the  steam  steadily  decreases  as  the  pressure  increases, 
but  after  the  critical  point  is  passed,  the  total  quantity  of  heat 
required  to  produce  the  steam  also  steadily  decreases.  Table  VIII. 
gives  what  are  called  the  properties  of  saturated  steam,  the  tempera- 
tures, corresponding  to  each  pressure,  the  latent  heat,  volume  of  each 
pound  of  steam,  etc. 


24      STEAM   BOILERS,   ENGINES,   AND   TURBINES 


TABLE  VIII. 

PROPERTIES  OF  SATURATED  STEAM. 


Absolute 
pressure 
in  Ib.  per 
eq.  in. 

Temperature 
or  boiling 
point  in  de- 
grees F. 

Total  heat  in 
thermal  units 
per  Ib.  of  steam 
from  0°  F. 

Latent  heat  in 
thermal  units 
per  Ib. 

Volume  (cubic 
feet  per  Ib.). 

Weight  of  1 
cubic  foot  of 
steam  in  Ib. 

Cubic  feet  of 
steam  from  1 
cubic  foot  of 
water  at  62°  F. 

1 

102-0 

1145-0 

1042-9 

330-36 

0-0030 

20,600 

2 

126-4 

1152-2 

1025-8 

172-08 

0-0058 

10,730 

4 

153-1 

1160-1 

1006-8 

89-62 

0-0112 

5,589 

5 

162-3 

1163-0 

1000-3 

72-66 

0-0138 

4,580 

8 

183-0 

1169-2 

985-7 

46-69 

0-0214 

2,911 

10 

193-3 

1172-3 

978-4 

37-84 

0-0264 

2,360 

12 

202-0 

1175-0 

972-2 

31-88 

0-0314 

1,988 

15 

213-1 

1178-4 

964-3 

25-85 

0-0387 

1,611 

18 

222-5 

1181-2 

957-7 

21-78 

0-0459 

1,357 

20 

228-0 

1182-9 

952-8 

19-72 

0-0507 

1,229 

22 

233-3 

1184-5 

949-9 

18-03 

0-0555 

1,123 

25 

240-5 

1186-6 

945-3 

15-99 

0-0625 

996 

30 

250-5 

1189-8 

937-9 

13-46 

0-0743 

838 

35 

259-4 

1192-5 

931-6 

11-65 

0-0858 

726 

40 

267-0 

1194-9 

926-0 

10-27 

0-0974 

640 

45 

274-5 

1197-1 

920-9 

9-18 

0-1089 

572 

50 

281-0 

1199-1 

916-3 

8-31 

0-1202 

518 

55 

287-1 

1201-0 

912-0 

7-61 

0-1314 

474 

60 

292-6 

1202-7 

908-0 

7-01 

0-1425 

437 

65 

298-0 

1204-3 

904-2 

6-49 

0-1538 

405 

70 

302-8 

1205-8 

900-8 

6-07 

0-1648 

378 

75 

307-5 

1207-2 

897-5 

5-68 

0-1759 

353 

80 

312-1 

1208-5 

894-3 

5-35 

0-1869 

333 

85 

316-1 

1209-9 

891-4 

5-05 

0-1980 

314 

90 

320-3 

1211-1 

888-5 

4-79 

0-2089 

298 

95 

324-0 

1212-3 

885-8 

4-55 

0-2198 

283 

100 

327-7 

1213-4 

883-1 

4-33 

0-2307 

270 

105 

331-2 

1214-4 

880-7 

4-14 

0-2414 

257 

110 

334-6 

1215-5 

878-3 

3-97 

0-2521 

247 

115 

337-9 

1216-5 

875-9 

3-80 

0-2628 

237 

120 

341-1 

1217-4 

873-7 

3-65 

0-2738 

227 

125 

344-2 

1218-4 

871-5 

3-51 

0-2845 

219 

130 

347-2 

1219-3 

869-4 

3-38 

0-2955 

211 

135 

350-1 

1220-2 

867-4 

3-27 

0-3060 

203 

140 

352-9 

1221-0 

865-4 

3-16 

0-3162 

197 

145 

355-6 

1221-9 

863-5 

3-06 

0-3273 

190 

150 

358-3 

1222-7 

861-5 

2-96 

0-3377 

184 

155 

361-0 

1223-5 

859-7 

2-87 

0-3484 

179 

160 

363-4 

1224-2 

857-9 

2-79 

0-3590 

174 

165 

366-0 

1224-9 

856-2 

2-71 

0-3695 

169 

170 

368-3 

1225-7 

854-5 

2-63 

0-3798 

164 

175 

370-8 

1226-4 

852-9 

2-56 

0-3899 

159 

180 

373-0 

1227-1 

851-3 

2-49 

0-4009 

155 

185 

375-3 

1227-8 

849-6 

2-43 

0-4117 

151 

190 

377-5 

1228-5 

848-0 

2-37 

0-4222 

148 

195 

379-6 

1229-2 

846-5 

2-31 

0-4327 

144 

200 

381-8 

1229-8 

845-0 

2-26 

0-4431 

141 

210 

385-8 

1231-1 

841-9 

2-16 

0-4634 

135 

i 

INTRODUCTORY  25 


Air 

Atmospheric  air  is  a  mixture  of  gases,  principally  oxygen  and 
nitrogen,  in  the  proportion  approximately  of  79  per  cent,  of  nitrogen 
to  21  per  cent,  of  oxygen.  As  mentioned  in  a  previous  paragraph 
also,  atmospheric  air  nearly  always  contains  a  certain  quantity  of  the 
vapour  of  water.  Water  is  always  being  evaporated  from  the  surfaces 
of  oceans,  rivers,  and  the  land,  the  vapour  so  formed  becoming  the 
clouds  we  see  in  temperate  and  cold  regions,  the  fogs  we  are 
unfortunately  so  familiar  with  in  this  country,  and  later  becoming 
rain,  sleet,  and  snow.  Air  has  very  much  the  same  properties  with 
regard  to  other  gases,  and  to  minute  particles  of  solid  matter,  that 
water  has.  As  explained  above,  gases  and  liquids  are  both  fluids  in 
scientific  language,  and  have  a  great  many  properties  alike.  One 
property  is  the  ability  to  absorb  other  vapours,  and  solid  matter  in 
a  finely  divided  state,  also  the  different  bacilli,  disease  germs,  and 
minute  animalcules  of  all  kinds.  The  quantity  of  the  vapour  of  water 
that  air  can  absorb  varies  with  the  temperature,  but  the  law  is  a  very 
peculiar  one.  It  follows  a  parabolic  curve.  The  percentage  of  the 
vapour  of  water  that  the  air  can  absorb  at  low  temperatures,  is  very 
small,  amounting  to  1£  grains  per  cubic  foot  at  20°  F.,  and  it  in- 
creases very  slowly  up  to  a  temperature  of  60°  F.,  when  it  increases 
more  rapidly.  The  presence  of  the  vapour  of  water  in  air  has  a  very 
important  bearing  upon  the  feeding  of  the  furnaces  of  steam  boilers 
with  air.  When  watery  vapour  is  present  in  air,  it  is  there  at  the 
expense  of  a  portion  of  the  volume  that  would  otherwise  be  occupied 
by  the  air.  Thus  if  2  per  cent  of  water  is  present  in  a  cubic  foot  of 
air,  it  means  that  the  actual  quantity  of  air  is  only  1692*44  cubic 
inches,  instead  of  1728,  and  that  therefore  in  place  of  362*9  cubic  inches 
of  oxygen  being  delivered  to  the  furnace,  only  290*3  cubic  inches 
are  delivered. 

As  already  explained  also,  air  expands  and  contracts  ^h  of  its 
volume  for  every  degree  C.,  and  ^T  for  every  degree  F.  This  means 
that  as  the  temperature  of  the  air  increases,  the  quantity  of  air 
present,  and  therefore  the  quantity  of  oxygen  present,  decreases  in 
this  proportion,  so  that  when  air  of,  say,  80°  F.  temperature  is  fed 
to  a  boiler  furnace,  it  only  delivers  0 '01 545  Ib.  weight  of  oxygen  per 
cubic  foot  as  against  0 '01 604  Ib.  weight  per  cubic  foot  at  60°  F.,  and 
this  is  irrespective  of  the  quantity  of  moisture  the  air  may  contain. 
These  figures  may  seem  small,  but  they  become  serious,  when 
millions  of  cubic  feet  are  dealt  with.  Table  IX.  gives  the  weight 


26      STEAM   BOILERS,   ENGINES,  AND   TURBINES 


TABLE  IX. 

VOLUME  AND  WEIGHT  OP  AIR  AT  VABIOUS  TEMPERATURES,  AND  ATMOSPHERIC 
PRESSURE  (STIRLING  BOILER  Co.). 


Temperature  in 
degrees  Fahrenheit. 

Volume  of  1  Ib.  cubic 
foot. 

Weight  of  1  cubic  foot 
in  pounds. 

50 

12-840 

0-077884 

55 

12-964 

0-077133 

60 

13-090 

0-076400 

65 

13-216 

0-075667 

70 

13-342 

0-074950 

75 

13-467 

0-074260 

80 

13-593 

•  0-073565 

85 

13-718 

0-072894 

90 

13-845 

0-072230 

95 

13-970 

0-071580 

100 

14-096 

0-070942 

110 

14-346 

0-069698 

120 

14-598 

0-068500 

130 

14-849 

0-067342 

140 

15-100 

0-066221 

150 

15-352 

0-065140 

160 

15-603 

0-064088 

170 

15-854 

0-063072 

180 

16-106 

0-062090 

190 

16-357 

0-061134 

200 

16-606 

0-060210 

210           16-860           0-059313 

212           16-910           0-059135 

220           17-111           0-058442 

230 

17-362           0-057596 

240 

17-612           0-056774 

250 

17-865           0-055975 

260 

18-116           0-055200 

370 

18-367           0-054444 

280 

18-621           0-053710 

290 

18-870           0-052994 

800 

19-121           0-052297 

320 

19-624           0-050959 

340 

20-126           0-049686 

360 

20-630           0-048476 

380 

21-131           0-047323 

400           21-634           0-046223 

425           22-262           0-044920 

450           22-890           0-043686 

475           23-518           0-042520 

500 

24-146        -   0-041414 

525 

24-775 

0-040364 

550 

25-403 

0-039365 

575 

26-031 

0-038415 

600 

26-659 

0-037510 

650 

27-913 

0-035822 

700 

29-172 

0-034280 

750 

30-428 

0-032865 

INTRODUCTORY  27 

and  volume  of  air  at  different  temperatures.  If  the  air  entering 
the  boiler  furnace  is  very  moist,  containing,  say,  10  per  cent,  of 
watery  vapour,  and  it  is  at  a  temperature  of,  say,  100°  F.,  the 
weight  of  oxygen  delivered  to  the  furnace  per  cuhic  foot  of  air 
passing  in,  is  only  0*0134  Ib.  instead  of  0*01604  with  dry  air  at  60°. 
The  quantity  of  the  vapour  of  water  present  in  the  air  varies  with  the 
climate  and  with  the  seasons.  In  this  country  the  largest  proportion 
of  the  possible  quantity  of  vapour  is  present  in  the  air  during  the 
winter  months,  the  proportion  being,  according  to  Box,  66*1  per  cent, 
of  the  possible  quantity  in  August,  68*5  in  July,  71/0  in  June,  81*0  in 
February,  85*8  in  January,  85*6  in  November,  and  86*8  in  December. 
On  the  other  hand,  the  quantity  of  moisture  the  air  can  carry  is 
highest  during  the  hot  summer  months  of  July  and  August,  and  is 
lowest  in  the  winter  months.  The  quantity  of  moisture  that  the  air 
can  carry,  as  already  explained,  depends  upon  the  temperature,  in 
accordance  with  the  law  mentioned  on  p.  25,  and  it  depends  upon  the 
elastic  force  of  the  vapour  of  water  at  that  temperature.  At  212°  F. 
the  elastic  force  of  the  vapour  is  29*962,  this  being  the  point  at  which 
vapour  comes  away  freely,  as  already  explained,  in  the  process  of 
boiling,  this  figure  and  the  following  ones  being  for  the  standard 
atmospheric  pressure.  At  102°  F.  the  elastic  force  of  the  vapour,  or  the 
vapour  pressure,  as  it  is  often  expressed,  is  =  2*036  inches  of  mercury, 
or  0-968  Ib.  per  sq.  in.  At  92°  F.  it  is  =  1-501,  or  0736  Ib.  per  sq. 
in. ;  at  82°  it  is  1*092,  or  0*54  Ib.  per  sq.  in.;  at  72°  it  is  0'785,  or  0*39  Ib. 
per  sq.  in. ;  at  62°  it  is  0*556,  or  0*276  Ib.  per  sq.  in ;  at  52°  it  is  0*388, 
or  0*194  Ib. per  sq.  in. ;  at  42°  it  is  0*267,  or  0133  Ib.  per  sq.  in.;  and 
at  32°  it  is  0*181,  or  0*09  Ib.  per  sq.  in.  It  will  be  seen  from  the  above 
figures,  that  though  the  percentage  of  the  possible  moisture  that  can 
be  carried  by  the  air  is  greatest  in  winter,  the  actual  quantity  may 
be  smaller  at  the  low  temperatures  prevalent.  Thus,  taking  a  tempe- 
rature of  42°  when  the  vapour  pressure  is  0*267,  and  taking  a  per- 
centage of  saturation  80  per  cent.,  or  the  possible  quantity  of  vapour 
that  may  be  carried,  the  actual  quantity  present  will  represent  a 
vapour  pressure  of  0*227  inch  of  mercury;  while  at  92°,  with  a 
percentage  of  66,  the  actual  quantity  present  will  represent  a  vapour 
pressure  of  0*99,  or  roughly  4J  times  that  present  with  the  lower 
winter  temperatures.  In  the  experiments  made  by  Mr.  Gayley  at 
Pittsburgh,  when  he  was  working  out  the  arrangement  for  drying 
the  air  for  the  blast  furnaces  that  he  has  since  established,  he  found 
different  quantities  of  vapour  present  in  the  air  at  different  times, 
the  variation  following  the  rules  given  above  very  largely,  but  there 
being  large  variations  from  day  to  day,  and  from  hour  to  hour. 

It  will  be  understood,  from  what  has  gone  before,  that  the 
pressure  of  the  air,  as  distinguished  from  the  pressure  of  the  com- 
bined mass  of  air  and  water  in  the  atmosphere,  will  be  the  average 


28       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

pressure  at  the  height  where  the  boiler  and  engine  is  fixed,  less  the 
pressure  of  the  water  vapour,  and  that  the  weight  of  air  passing 
into  a  furnace,  and  therefore  the  weight  of  oxygen,  will  follow 
this  law. 


Measuring  the  Percentage  of  Vapour  in  Air 

The  percentage  of  vapour  present  in  air  is  measured  by  taking 
the  difference  in  the  readings  between  two  thermometers,  one  of 
which  is  exposed  to  the  ordinary  temperature  of  the  air,  the  other 
being  exposed  to  the  cooling  effect  of  the  evaporation  of  water. 
The  usual  method  is — two  thermometers  are  fixed  side  by  side,  one 
being  exposed  to  the  ordinary  temperature  of  the  air,  and  the 
other  having  some  textile  porous  fabric,  such  as  a  piece  of  waste, 
or  tow  wrapped  round  its  bulb,  the  waste  dipping  into  a  vessel 
containing  water.  The  evaporation  of  the  water  contained  in  the 
waste  extracts  heat  from  the  bulb  of  the  thermometer,  and  lowers 
the  reading  shown  by  it,  the  evaporation  being  directly  in  proportion 
to  the  difference  between  the  percentage  of  saturation  of  the  air,  and 
full  saturation.  From  the  difference  between  these  two  readings,  the 
percentage  of  saturation  may  be  obtained  by  a  table  that  was  worked 
out  by  Mr.  Glaisher  at  Greenwich  some  years  ago,  and  is  given 
below. 

TABLE   X. 


Degrees  of  cold  in  the  wet-bulb  thermometer. 


IS!- 

2  3 

4567 

8  |  9 

10 

11 

12 

13 

14 

15|l6 

17 

18  1  19  j  20  21  j  22  23 

Degrees  of  humidity,  saturation  being  100. 


32° 

07 

75 

1 

42° 

92 

85 

78 

72 

66,60 

54 

49 

44 

40 

36 

33 

30 

27 

—  i  — 









;  

52° 

93 

86 

80 

74 

69164 

59 

54 

50 

46 

42 

39 

36 

33 

30J27 

25 

— 

— 

— 

—  —  

62° 

94 

88 

82 

77 

72  67 

62 

58 

54 

50 

47 

44 

41 

38 

35!  32 

30 

28 

26 

— 



72° 

94 

89 

8.4 

79 

74,69 

65 

61. 

57 

54 

51 

48 

45 

42 

39i36 

34 

32 

30 

28 

26  24  23 

82° 

95 

90 

85 

80 

76  72 

68 

64 

60 

57 

54 

51 

48 

45 

42  140 

38 

35 

33 

31 

29  i  27  26 

The  above  method  is  known  as  that  of'  the  wet  and  dry  bulb,  but 
when  carried  out  as  described,  it  is  open  to  grave  objections,  which 
affect  its  accuracy.  When  the  two  thermometers  merely  stand  side 
by  side,  with  the  air  not  in  motion  about  them,  the  full  effect  of  the 
unsatisfied  saturation  of  the  air  is  not  obtained,  the  effect  of  the  air 
upon  the  wet  bulb  being  masked  to  a  large  extent  by  the  layer  of 
still  air  immediately  in  contact  with  it.  It  will  be  understood,  from 


INTRODUCTORY  29 

what  lias  been  explained  about  the  saturation  of  air,  that  if  the  air 
immediately  surrounding  the  bulb,  becomes  itself  saturated,  and 
is  not  moved  away,  evaporation  from  the  fabric  surrounding  the 
bulb  will  then  cease,  and  an  apparent  measurement  will  be  taken, 
showing  the  hygrometric  state  of  the  atmosphere  at  a  higher 
point  of  saturation  than  it  really  is.  To  meet  this  difficulty,  two 
methods  have  been  adopted.  The  air  in  the  neighbourhood  of  the 
two  thermometers  may  be  simply  agitated  with  a  fan,  so  that  the 
masking  layer  of  still  air  is  disturbed,  and  something  like  a  convection 
current  set  up.  A  more  satisfactory  method,  however,  which  the 
author  believes  comes  to  us  from  America,  consists  in  mounting  the 
two  thermometers  together  on  a  handle  arranged  for  whirling  round 
the  heat  on  the  lines  of  some  children's  toys.  One  of  the  thermo- 
meters has  its  bulb  surrounded  by  a  moistened  pad,  as  before,  and 
the  two  are  whirled  rapidly  round  the  head,  in  the  body  of  the  air 
whose  hygrometric  state  is  to  be  measured,  for  several  seconds,  and 
the  readings  then  taken,  and  these  are  stated  to  be  as  correct  as  can 
be  obtained. 

Volume  and   Pressure 

The  volume  of  air  varies  inversely  with  the  pressure,  in  accord- 
ance with  the  following  formula :  pv  =  a  constant.  That  is  to  say, 
the  product  of  the  two  factors,  p  and  v,  representing  respectively 
pressure  and  volume,  is  constant.  If  the  pressure  increases,  the 
volume  decreases  in  the  same  proportion.  Thus,  compressing  air  to 
double  its  previous  pressure,  reduces  its  volume  to  half,  and  vice  versa. 

This,  again,  is  of  importance  when  air  is  delivered  to  a  furnace 
under  pressure,  as  any  pressure  to  which  it  is  subject  will  reduce  its 
volume.  When  air  is  compressed,  heat  is  liberated  in  the  air,  the 
heat  representing  the  energy  expended  upon  the  air  in  the  act  of 
compression,  and  the  heat  delivered  to  the  air  expands  it  in  the 
proportion  given  above,  so  that  any  force  which  tends  to  compress 
the  air,  such  as  the  apparatus  employed  in  forced  draught,  or  the 
increase  of  barometric  pressure,  tends  at  the  same  time  to  diminish 
the  volume  of  the  air  by  the  increased  pressure,  and  by  liberating 
heat  in  the  air,  to  increase  the  volume  of  the  compressed  air,  and  so 
to  resist  the  act  of  compression. 

The  Specific   Heat  of  Air 

The  specific  heat  of  air  is  usually  given  in  two  forms,  under  con-- 
stant  pressure,  and  under  constant  volume.  The  specific  heat  of  air  at 
constant  pressure  is  usually  taken  as  0*238,  and  at  constant  volume, 
0'169,  water  being  taken  as  unity.  It  should  be  mentioned,  however, 


30       STEAM   BOILERS,   ENGINES,   AND    TURBINES 

that  the  specific  heat  of  air  is  often  taken  as  unity  for  comparison 
with  that  of  gases.  When  air  and  other  gases  are  heated  in  closed 
vessels,  so  that  expansion  cannot  take  place,  and  the  pressure  is 
necessarily  increased,  a  smaller  quantity  of  heat  will  raise  the 
temperature  of  the  air  by  1°  F.  than  when  the  air  is  allowed  to 
expand  so  as  to  maintain  its  volume  constant.  This  is  the  explana- 
tion of  the  two  figures  given.  In  practice,  air  is  never  heated  under 
constant  pressure,  and  never  so  that  it  can  maintain  its  volume 
constant,  the  conditions  usually  being  that  both  pressure  and  volume 
are  increasing,  so  that  the  actual  specific  heat  of  the  air  is  somewhere 
between  the  two  figures,  and  it  will  not  be  far  wrong  to  take  it  as 
about  0*2.  The  following  table  gives  the  specific  heat  of  the*  other 
gases  that  are  met  with  in  boiler  work — 

TABLE  XI. 


Specific  heat  at 

Specific  heat  at 

constant  pressure. 

constant  volume. 

Oxygen  gas 

0-2182 

0-1542 

Hydrogen  gas  . 
Nitrogen  gas    . 

3-4046 
0-244 

2-4200 
0-1717 

Carbonic  acid  . 

0-2164 

0-1617 

,,        oxide 

0-2479 

0-1737 

Vapour  of  water 

0-475 

0-3624 

The  very  high  specific  heat  of  hydrogen  gas  will  be  noted,  and 
its  great  importance,  if  free  hydrogen  is  present,  in  any  process  of 
combustion. 

The  specific  heat  of  air  varies  also  with  the  pressure,  both  with 
constant  pressure  and  constant  volume.  The  variations  are  given  in 


the  followin    table  — 


TABLE   XII. 


Pressure  in  inches  of 

Specific  heat  with  pres- 
sure constant  and 

Specific  heat  with 
volume  constant  and 

mercury. 

volume  variable. 

pressure  variable. 

1 

1-303 

0-9170 

5 

0-5827 

0-4101 

10 

0-4121 

0-2900 

20 

0-2914 

0-2050 

29-92 

0-238 

0-169 

40 

0-2061 

0-145 

60 

0-168 

0-1184 

80 

0-1457 

0-1025 

100 

0-1306 

0-0919 

180 

0-0971 

0-0684 

300 

0-0752 

0-0529 

INTRODUCTORY  31 

The  importance  of  this  table  comes  in  with  high  pressures  in  the 
boiler,  and  with  low  pressures  in  the  condenser.  With  high  pressures, 
the  air  with  which  the  gases  formed  by  combustion  are  diluted,  absorb 
a  smaller  quantity  of  heat  to  raise  them  to  the  furnace  temperature, 
and  in  the  condenser  the  air  present  will  absorb  a  larger  quantity  of 
heat  than  at  ordinary  atmospheric  pressures. 


Water 

Water  is  a  chemical  compound  of  hydrogen  and  oxygen  gases, 
the  formula  being  H20,  two  molecules  of  hydrogen  combining  with 
one  molecule  of  oxygen  to  form  one  molecule  of  water.  By  weight, 
16  parts  of  oxygen  combine  with  2  parts  of  hydrogen.  As  already 
explained,  water  exists  in  all  three  states,  in  the  solid  state  as 
ice  and  as  snow ;  in  the  liquid  state  as  water ;  in  the  gaseous  state 
as  steam,  and  in  a  not  quite  understood  state  as  vapour.  Water 
has  the  important  property  of  dissolving  almost  every  known 
substance,  solid,  liquid,  and  gaseous.  Water  comes  to  us  originally 
from  the  clouds.  As  explained,  evaporation  is  constantly  taking 
place  from  the  oceans,  rivers,  and  the  surface  of  the  earth,  the 
evaporation  depending,  at  any  instant,  upon  the  temperature  of  the 
atmosphere,  and  upon  the  quantity  of  the  vapour  of  water  already 
present.  Put  in  another  way,  the  vapour  which  is  issuing  from  the 
water  on  the  earth's  crust  has  a  certain  tension  of  its  own,  and 
the  vapour  which  is  present  in  the  atmosphere  has  also  a  certain 
tension.  When  these  two  are  equal  no  evaporation  can  take  place  ; 
while  when  the  tension  of  the  vapour  issuing  from  the  water  is 
greater  than  that  of  the  vapour  present  in  the  air,  evaporation  goes 
on  more  or  less  freely,  approximately  in  proportion  to  the  difference 
between  the  two  vapour  tensions.  When  the  tension  of  the  vapour 
in  the  air  is  greater  than  that  of  the  vapour  issuing  from  the  water, 
evaporation  ceases,  and  some  of  the  moisture  present  in  the  atmosphere 
is  deposited  upon  the  ground  or  upon  the  water. 

As  explained  on  p.  27,  the  tension  of  the  vapour  issuing  from 
the  water  depends  upon  the  temperature  of  the  water,  while  the 
tension  of  the  vapour  already  present  in  the  atmosphere  depends 
upon  the  temperature  of  the  atmosphere,  and  the  percentage  of 
possible  vapour,  of  possible  saturation  by  vapour,  that  is  present. 
If  the  water  and  the  air  are  at  the  same  temperature,  and  the  air  is 
saturated,  neither  evaporation  nor  deposit  can  take  place.  And  the 
same  conditions  may  rule  if  the  temperature  of  the  water  is  com- 
paratively low,  while  the  temperature  of  the  air  is  comparatively 
high,  and  the  percentage  of  saturation  is  large.  The  formation  of 
dew  at  night  is  caused  by  the  ground  in  any  particular  position 


32       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

cooling  by  radiation  after  it  has  ceased  to  receive  the  sun's  rays,  the 
vapour  issuing  from  it  becoming  considerably  lowered  in  tension, 
while  the  vapour  of  the  air  above  it  may  have  a  considerable  tension, 
due  to  its  higher  temperature  and  to  its  state  of  saturation,  and 
deposit  then  takes  place. 

The  water  evaporated  from  the  earth  forms  into  clouds,  and  after- 
wards descends  as  rain,  falling  tirst  upon  the  high  lands,  the  clouds 
also  being  driven  before  the  winds  that  blow  from  time  to  time. 
The  water  that  descends  from  the  clouds,  if  in  the  form  of  rain, 
runs  down  the  surface  of  the  ground,  forming  rivulets,  which  deliver 
their  water  to  streams,  these  again  delivering  their  water  to  rivers, 
which  deliver  to  larger  rivers,  and  so  on,  the  large  rivers  delivering 
to  the  oceans.  But  a  considerable  portion  of  the  water  which  falls 
upon  the  surface  of  the  ground  sinks  into  it,  some  of  it  going  to 
nourish  the  plants,  etc.,  that  are  growing,  and  some  falling  upon 
what  are  called  the  water-bearing  strata,  which  outcrop  at  the  surface 
of  the  ground  in  various  positions,  and  usually  descend  into  the 
ground  at  an  angle  with  the  vertical.  The  water  that  is  obtained 
by  sinking  wells,  is  that  which  has  fallen  upon  the  outcrop  of  the 
water-bearing  strata,  and  has  descended  through  it  to  different  depths. 
Water-bearing  strata  are  the  porous  rocks,  such  as  sandstone,  and 
the  loose  earths,  such  as  gravels,  and  some  kinds  of  sand. 

The  reservoirs  that  are  made  for  the  supply  of  water  to  towns, 
are  formed  by  collecting  all  the  streamlets  running  down  the  sides 
of  the  hills  in  the  high  lands  above  the  towns  over  a  considerable 
area,  and  preventing  their  running  away  in  the  streams,  etc.,  as 
mentioned  above,  by  fixing  dams  across  convenient  spots,  such  as 
the  junctions  of  two  or  more  valleys,  where  a  considerable  depth  of 
water  can  be  impounded,  the  water  being  carried  from  there  by  pipes 
into  the  town. 

The  water  which  runs  down  the  sides  of  hills  and  mountains,  and 
at  the  bottoms  of  valleys  in  streams  and  rivers,  dissolves  a  certain 
portion  of  the  substance  of  the  rocks,  etc.,  over  which  it  runs,  and 
also  carries  off  a  certain  quantity,  in  a  finely  divided  state,  the  friction 
of  the  running  water  loosening  some  of  the  particles  of  the  rock  or 
earth  over  which  it  is  running,  and  the  running  stream  carrying  the 
particles  along  with  it.  The  ability  of  water  to  dissolve  portions  of 
the  rocks,  etc.,  over  which  it  runs,  leads  to  the  formation  of  the 
natural  mineral  springs  that  are  found  all  over  the  world,  having 
certain  medicinal  properties,  and  it  also  leads  to  the  waters  employed 
for  boiler  purposes  containing  the  salts,  mainly  of  lime,  magnesium, 
and  sodium,  which  confer  on  the  water  the  property  known  as 
hardness. 

Water  has  also  the  property  of  dissolving  pretty  well  all  gases 
and  liquids,  and  there  is  a  peculiar  feature  in  connection  with  the 


INTRODUCTORY  33 

solution  of  gases  in  water.  Gases,  it  will  be  remembered,  exist  in 
the  gaseous  state,  because  they  are  possessed  of  a  certain  quantity  of 
latent  heat.  When  a  gas  is  dissolved  in  water,  it  delivers  its  latent 
heat  to  the  water,  in  the  process  of  solution,  the  water  being  heated 
by  the  liberated  latent  heat. 


Impurities  in  Water 

As  will  be  seen  when  dealing  with  boilers,  the  impurities  which 
the  water  collects  in  its  passage  over  rocks,  etc.,  have  a  very  serious 
effect  upon  the  heating  power  of  boilers,  inasmuch  as  the  substances 
carried  by  the  water,  whether  in  solution  or  mechanically,  are  deposited 
upon  the  water  side  of  the  heating  surfaces,  and  gradually  build  up 
a  scale  that  offers  considerable  resistance  to  the  passage  of  the  heat 
through  the  metal  separating  the  water  and  the  hot  gases.  The 
principal  substances  found  in  water  are  the  carbonates  and  sulphates 
of  calcium  and  magnesium,  CaC03  and  MgC03,  CaS04  and  MgS04. 
Other  substances  that  are  found  frequently  are  the  carbonates  of 
iron,  Fe2C03,  and  the  chlorides  of  calcium,  magnesium,  potassium,  and 
sodium,  CaCl2,  MgCl2,  KC1,  NaCl.  Sodium  chloride  is  the  principal 
foreign  component  of  sea  water. 

The  apparatus  for  dealing  with  impurities  in  the  water  with 
which  boilers  are  to  be  fed,  are  dealt  with  in  their  section,  on  p. 
182.  They  operate  principally  by  the  application  of  heat,  and  the 
addition  of  certain  substances  which  render  the  dissolved  salts  in  the 
water  insoluble,  and  precipitate  them  before  the  water  is  allowed  to 
enter  the  boiler.  The  carbonates  are  not  soluble  in  water,  but  the 
bi-carbonates  are.  The  carbonates  are  the  salts  given  above,  in 
which  only  one  molecule  of  carbonic  acid  is  present  in  combination, 
but  the  bi-carbonates  have  two  molecules  of  carbonic  acid,  the  addition 
of  the  second  molecule  rendering  them  soluble  in  water.  The  applica- 
tion of  heat  to  the  water  drives  off  the  additional  molecule  of  carbonic 
acid,  and  the  carbonate  is  then  deposited.  If  the  carbonic  acid  is 
removed  from  the  water  before  it  enters  the  boiler,  and  the  carbonates 
are  allowed  to  deposit  in  some  vessel  outside  of  the  boiler,  the  water 
is  rendered  harmless  so  far  as  those  salts  are  concerned ;  but  if  the 
water  is  allowed  to  enter  the  boiler  with  the  bi-carbonates  in  solution, 
as  the  second  molecule  is  driven  off  at  a  maximum  temperature  of 
290°  F.,  or  when  the  steam  is  at  a  pressure  of  58  Ibs.  absolute,  or 
43  Ibs.  gauge,  the  carbonates  remaining  are  deposited  on  the  metal 
in  the  water  space  itself.  The  sulphates  and  chlorides  are  got  rid  of 
by  the  addition  of  carbonate  of  soda,  NaC03,  and  caustic  lime,  CaH20, 
in  proportions  depending  upon  the  quantity  of  the  salts  present. 

D 


34      STEAM   BOILERS,    ENGINES,   AND    TURBINES 

The  presence  of  the  impurities  in  the  water  lead  to  other  troubles, 
such  as  priming,  etc.,  that  will  be  dealt  with  when  describing  boilers 
and  their  working. 


Steam 

As  already  explained,  steam  is  water  in  the  gaseous  state,  and  is 
produced  from  water  by  the  application  of  heat,  different  quantities 
of  heat  being  required  to  evaporate  a  given  quantity  of  water, 
according  to  the  pressure  to  which  the  surface  of  the  water  is 
exposed,  and  according  to  the  percentage  of  salts  held  in  solution  in 
the  water. 

Steam  as  it  comes  away  from  the  surface  of  water  in  the  boiler, 
is  known  as  saturated  steam.  The  term  "  saturated  "  means  here,  that 
the  steam  is  of  the  maximum  density  at  the  particular  temperature. 
In  the  table  of  the  properties  of  saturated  steam  given  on  p.  124,  it 
will  be  noted  that  the  temperature,  the  latent  heat,  the  total  heat,  the 
volume  per  cubic  foot,  the  weight  per  cubic  foot,  and  the  quantity  of 
steam  produced  from  one  cubic  foot  of  water  are  given  in  the  successive 
columns.  The  volume  per  cubic  foot  is,  of  course,  only  another  name 
for  its  density,  and  it  will  be  noticed  that  the  volume  steadily  decreases, 
the  density  increasing  in  the  same  proportion  as  the  pressure  increases. 
Thus  at  1  Ib.  per  square  inch  absolute  pressure,  the  volume  is  3304 
cubic  feet  per  pound,  at  2  Ibs.  pressure  it  is  only  172  cubic  feet ;  at  10 
Ibs.  it  is  37'8  cubic  feet ;  at  14*7  Ibs.,  or  atmospheric  pressure,  it  is 
26-37  cubic  feet;  at  50  Ibs.  it  is  8'34  cubic  feet;  at  100  Ibs.  it  is 
4'34,  and  at  200  Ibs.  it  is  2*26,  and  so  on.  Saturated  steam  has 
certain  properties  of  its  own,  in  particular,  with  reference  to  the 
transmission  of  heat  through  iron  pipes.  According  to  Professor 
Siebel,  the  authority  on  refrigeration,  the  rate  of  transmission  of  heat 
from  saturated  steam  through  an  iron  pipe  to  water  on  the  other  side 
of  the  pipe,  is  only  one  quarter  that  at  which  heat  is  transmitted  from 
hot  water  in  an  iron  pipe,  to  water  on  the  other  side  of  the  pipe. 
Saturated  steam,  however,  is  very  rarely  pure  steam.  That  is  to  say, 
taking  steam  to  be  a  gas,  and  to  have  all  the  properties  pertaining  to 
gases,  the  steam  from  steam  boilers  carries  in  it  the  vapour  of  water, 
or  finely  divided  globules  of  water,  very  much  in  the  same  way  as  air 
carries  the  vapour  of  water,  as  already  explained.  The  vapour  of 
water,  or  the  globules  of  water  held  in  suspension,  introduce  a  source 
of  loss  in  steam  engines,  owing  to  the  facility  with  which  on  the 
steam  meeting  surfaces  of  slightly  lower  temperature  than  itself,  the 
water  carried  in  suspension  condenses  on  those  surfaces,  being  after- 
wards formed  into  steam  at  the  expense  of  heat  taken  from  the  metal 
surfaces  upon  which  they  were  condensed. 


INTRODUCTORY  35 


Superheated   Steam 

To  meet  the  above  difficulty  of  the  condensation  of  the  water 
carried  over  from  the  boiler,  it  is  now  common  to  subject  steam  on 
its  way  to  the  engine,  or  turbine  that  is  to  use  it,  to  a  process  known 
as  superheating.  Various  forms  of  superheaters  are  described  later 
in  the  book,  but  the  object  of  all  is,  the  heating  of  the  steam,  out  of 
contact  with  the  water  from  which  it  was  formed,  and  the  formation 
of  all  the  watery  globules,  or  watery  vapour  that  is  carried  in  sus- 
pension, into  proper  steam  at  the  pressure  and  temperature  of  the 
steam  which  carries  it.  The  process  of  superheating  confers  certain 
valuable  properties  upon  the  steam,  that  it  does  not  possess  in  the 
saturated  form.  Superheated  steam,  according  to  Professor  Siebel, 
transmits  heat  through  an  iron  pipe,  to  water  on  the  other  side  of  the 
pipe,  at  only  £l0th  the  rate  that  saturated  steam  does.  It  need  hardly 
be  pointed  out  what  a  very  valuable  property  this  is,  in  all  apparatus 
where  work  is  to  be  obtained  from  steam  by  its  expansion,  and  by 
mechanical  work  obtained  in  the  process  of  expansion.  Any  heat 
the  steam  loses  by  conduction  to  the  cylinder  or  pipes  through  which 
it  passes,  robs  it  of  a  portion  of  the  energy  it  would  expend  in  driving 
the  piston,  or  in  turning  the  blade  of  a  turbine  wheel.  In  addition 
to  the  above,  the  specific  heat  of  steam  being  only  about  0'5,  the 
steam  produced  from  a  pound  of  water  will  have  its  temperature 
raised  in  the  proportion  of  2  to  1,  about,  by  the  application  to  it 
of  any  definite  quantity  of  heat.  If  the  steam  to  be  superheated 
is  in  a  closed  vessel,  unable  to  escape,  as  when  the  engines  are  not 
taking  steam,  the  application  of  heat  in  the  process  of  superheating 
will  raise  the  pressure  of  the  steam,  with  the  temperature,  the  pressure 
and  temperature  of  steam  going  together  in  accordance  with  the  figures 
given  in  Table  8.  Where,  as  will  more  usually  be  the  case,  the  steam 
is  superheated  on  its  way  from  the  boiler  to  the  engines,  and  is  there- 
fore free  to  expand,  its  volume  will  increase  with  the  application  of 
heat,  in  the  same  proportion  as  its  pressure  would  if  confined.  In 
considering  the  question  of  superheating,  it  is  important  to  know  the 
quantity  of  vapour  or  watery  globules  present  in  the  steam,  and  the 
superheating  apparatus,  whatever  it  may  be,  must  provide  sufficient 
heat  during  the  passage  of  the  steam  through  it,  to  raise  the  whole  of 
the  water  present  to  the  condition  of  proper  steam,  at  the  temperature 
to  which  the  steam  itself  is  raised.  In  practice,  the  maximum  quantity 
of  vapour  that  can  be  carried  over  by  the  steam,  under  ordinary  work- 
ing conditions,  is  found  by  test,  and  the  superheating  apparatus  is 
arranged  to  furnish  the  necessary  heat  required  for  converting  this 
maximum  quantity  of  water  into  steam  during  the  passage  of  the 
steam  through  the  superheater. 


36      STEAM   BOILERS,   ENGINES,  AND   TURBINES 


Specific   Heat  of  Superheated   Steam 

The  specific  heat  of  superheated  steam  at  atmospheric  pressure  is 
taken  at  0'48,  but  according  to  recent  measurements,  the  specific  heat 
of  steam,  superheated  to  100°  F.  above  the  saturated  state,  is  0*65,  and 
with  200°,  0'75.  It  is  frequently  taken  as  0*5  for  calculations. 

It  should  be  noted  that  the  remarks  made  above,  with  reference 
to  the  additional  work  to  be  got  out  of  superheated  steam,  owing  to 
the  lower  specific  heat,  applies  to  a  large  extent  to  steam  generated 
in  the  boiler,  at  higher  than  ordinary  atmospheric  pressure.  Modern 
practice  has  tended  to  gradually  increasing  steam  pressures.  In  the 
early  days  of  steam,  the  old  Cornish  pumping-engine  worked  at  only 
a  few  pounds  above  atmospheric  pressure,  the  vacuum  produced  by  con- 
densing under  the  piston  being  relied  on  very  largely  for  the  work 
done  by  the  engine.  Even  as  late  as  thirty  years  ago,  steam  pressures 
of  30  Ibs.  or  thereabouts,  were  very  common  all  over  the  United 
Kingdom.  Gradually,  however,  the  pressures  used  have  increased, 
first  to  50  Ibs.,  then  to  80  Ibs.,  and  now  pressures  of  250  Ibs,  per 
square  inch  are  not  uncommon,  and  the  increased  pressures  all  tend 
to  economy  in  coal,  partly  for  the  reason  given  in  connection  with  the 
superheating  of  steam,  because  the  specific  heat  of  steam  is  so  much 
lower  than  that  of  water,  and  partly  because,  as  mentioned  in  a 
previous  paragraph,  the  latent  heat  of  steam  steadily  decreases,  as 
the  pressure  increases.  And  it  is  the  latent  heat  which  forms  practi- 
cally the  great  source  of  waste  with  steam.  The  more  the  latent  heat 
can  be  reduced,  the  more  economical  is  the  use  of  steam,  providing 
that  the  energy  delivered  to  the  steam  is  economically  applied. 


Carnot's  Law  of  the  Efficiency  of  Heat  Engines 

The  law  of  the  efficiency  of  all  heat  engines,  steam,  gas,  etc., 
which  was  enunciated  by  the  French  savant  Carnot  some  eighty  years 
ago,  still  rules  in  the  heat-engine  world.  It  is  as  follows  :  — 

rp      _    m 

The  efficiency  =  —  ^  —  -.     The  formula  is  sometimes  written 


T     ' 

Where  TI  is  the  absolute  temperature  at  which  the  heat  is 
received  by  the  engine,  and  T2  is  the  absolute  temperature  at  which 
it  is  rejected. 

In  using  this  formula,  another  law  of  heat  operation  rules,  viz. 
that  the  final  result  of  successive  changes  of  heat  is  irrespective  of 
the  method  of  the  changes  and  the  steps.  In  the  case  of  steam,  the 


INTRODUCTORY  37 

law  may  be  applied  separately  to  the  boiler,  to  the  engine,  and  to  the 
condenser,  or,  as  is  more  usual,  it  may  be  applied  to  the  combination 
as  a  whole.  It  means  that  the  greater  the  difference  of  temperature 
between  the  steam  generated  by  the  boiler,  and  that  finally  ejected 
from  the  exhaust  of  the  engine,  the  higher  is  the  efficiency  of  the 
plant  as  a  whole,  the  greater  the  proportion  of  the  heat  delivered  to 
the  water  that  is  recovered  from  the  crank-shaft  of  the  engine,  or  the 
shaft  of  the  turbine.  The  law  may  be  carried  further  back  to  the 
temperature  of  the  furnace,  and  will  be  equally  applicable,  the  higher 
the  temperature  of  the  furnace  and  the  lower  the  temperature  of  the 
steam,  finally  ejected  from  the  exhaust,  the  higher  is  the  efficiency  of 
the  plant,  and  the  lower  the  consumption  of  coal  in  the  boiler  furnace 
per  B.H.P.  at  the  steam  motor-shaft  should  be. 

It  will  be  seen  that  this  law  explains  a  good  many  things  that  are 
at  first  somewhat  puzzling,  such  as  the  very  large  increase  of  efficiency 
obtained  from  the  steam  turbine  by  increased  vacuum,  and  the 
increased  efficiency  of  any  steam  plant,  with  higher  steam  pressures. 
The  above  is  subject  to  the  steam  and  the  heat  being  usefully  applied. 
Any  leakage  of  heat,  such  as  radiation  from,  the  boiler  surface,  from 
the  steam-pipes,  and  from  the  surface  of  the  engine  cylinders,  which 
all  go  to  increase  the  range  of  temperature,  decrease  the  efficiency  of 
the  heat  combination. 


Fuel  and  Combustion 

In  all  boiler  plant  heat  is  obtained  by  the  combustion  of  fuel  in 
a  furnace,  either  forming  part  of  or  attached  to  the  boiler.  By  com- 
bustion is  meant  the  chemical  combination  of  certain  components  of 
coal,  wood,  oil,  and  other  substances  with  oxygen.  As  the  author 
understands  the  matter,  gases  exist  in  the  gaseous  state  by  virtue  of 
the  fact  that  they  are  possessed  of  a  certain  quantity  of  energy, 
enabling  them  to  exist  as  gases ;  and  in  addition  to  this,  every  gas 
exists  as  that  gas  by  reason  of  the  possession  of  a  certain  quantity 
of  energy  peculiar  to  itself,  as  distinguished  from  its  own  latent 
heat.  Put  in  another  way,  the  energy  possessed  by  gases  of  different 
forms  varies  very  considerably.  The  energy  possessed  by  hydrogen 
gas  is  apparently  very  much  larger  than  that  of  any  other  gas. 
Oxygen  possesses  a  large  store  of  energy,  while  carbonic  acid  and 
carbonic  oxide  exist  with  a  very  much  smaller  quantity.  Hence, 
when  any  substance,  such  as  carbon,  combines  with  oxygen,  though 
a  certain  quantity  of  energy  is  demanded  to  convert  the  carbon  to 
the  gaseous  state,  the  energy  required  to  enable  carbonic  acid  to  exist 
as  a  gas,  is  so  much  less  than  that  required  for  the  existence  of 
oxygen  as  a  gas,  that  a  certain  quantity  of  energy  is  liberated  in  the 


38       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

form  of  heat.  The  quantity  of  energy  liberated  by  the  combination 
of  certain  substances  has  been  measured  by  different  experimenters, 
as  given  below. 

(1)  Carbon  oxidizing  to  carbonic  oxide,  4500  B.  Th.  units,  or 
2416  calories. 

(2)  Carbon  oxidizing  to  carbonic  acid,  14,500  B.  Th.  units,  or 
8080  calories. 

(3)  Hydrogen   combining  with   oxygen   to   form  water,    62,000 
B.  Th.  units,  or  34,180  calories. 

(4)  Sulphur  oxidizing  to  S02,  4000  B.  Th.  units. 

The  above  figures  for  the  calorific  values  are  to  be  taken  as 
approximate.  They  are  near  enough  for  all  practical  purposes,  and 
the  qualification  just  named  is  given  because  different  experimenters 
appear  to  have  obtained  different  results.  All  the  results  are  in  the 
close  neighbourhood  of  the  figures  given. 

The  heat  liberated  by  the  combination  of  other  elements  with 
oxygen  has  also  been  measured,  but  carbon  and  hydrogen  and  sulphur 
are  the  only  elements  that  concern  us.  All  known  fuels  owe  their 
useful  calorific  value  to  the  presence  of  these  elements.  Sulphur 
occurs  to  a  small  extent  in  coal,  but  its  combining  value  is  not  of 
great  importance.  It  is  always  eliminated  where  possible. 


Calorific  Power 

By  calorific  power  is  meant  the  heat  which  is  liberated  by  the 
combination  of  1  Ib.  of  the  substance  with  oxygen.  It  is  also  fre- 
quently written  as  "  calorific  value."  The  meaning  of  either  expres- 
sion is,  the  comparative  ability  of  the  different  substances  to  liberate 
heat,  when  a  definite  quantity  of  the  substance  combines  with  oxygen. 

The  calorific  powers  of  the  principal  fuels  have  been  determined 
by  careful  experiment.  They  all  depend  upon  the  quantity  of  carbon 
and  hydrogen  that  are  present  in  them,  modified  by  the  quantity  of 
oxygen  that  is  also  present  in  nearly  all  of  them.  Hydrogen  and 
oxygen  have  a  strong  affinity  for  each  other,  and  will  combine  to 
form  water  whenever  the  opportunity  occurs.  In  the  great  majority 
of  fuels,  while  a  certain  quantity  of  hydrogen  is  present,  a  certain 
quantity  of  oxygen  is  also  present,  and  before  the  calorific  value  of  a 
fuel  is  determined  theoretically,  the  quantity  of  hydrogen  required  to 
satisfy  the  quantity  of  oxygen  present  is  deducted  from  the  total 
quantity  of  hydrogen,  the  remainder  being  taken  with  the  carbon. 
Thus,  as  hydrogen  combines  with  eight  times  its  own  weight  of 
oxygen,  J  of  the  weight  of  oxygen  present  may  be  deducted  from  the 
weight  of  hydrogen.  Dulong's  formula  for  calculating  the  calorific 
value  of  any  fuel  is  as  follows : — 


INTRODUCTORY  39 

rl  =  14,554  C  +  61,524  (H- 9)  +  4000  S 

\  o/ 

where  C,  H,  0,  and  S  represent  the  proportionate  parts  of  carbon, 
hydrogen,  oxygen,  and  sulphur  respectively. 

Forms  of  Fuel 

The  available  fuels  are :  the  different  forms  of  coal,  wood,  the 
refuse  from  sugar-canes,  cotton  trees  and  similar  things,  peat,  petro- 
leum in  its  various  forms,  oils  of  various  kinds  other  than  petroleum, 
natural  gas,  blast  furnace  gas  and  producer  gas,  corn,  maize,  oak 
bark,  sugar.  Some  forms  of  dried  manure  and  other  substances  have 
all  been  used.  Any  substance,  in  fact,  containing  carbon,  or  carbon 
and  hydrogen,  may  be  employed  as  a  fuel,  providing  that  its  tempe- 
rature can  be  raised  to  ignition  point,  and  that  it  can  be  supplied 
with  oxygen. 

Coal 

Coal  is  found  at  various  depths  in  the  earth's  crust,  ranging  from 
0,  or  the  outcrop,  as  it  is  termed,  down  to  depths  of  1000  yards  at 
present  being  worked,  while  deposits  are  also  believed  to  exist  at  still 
greater  depths.     The  coal  has  all  been  formed  in  the  same  manner, 
so  far  as  is  known  at  present.     In  the  places  where  coal  beds  now 
exist,  plants  of  a  certain  character  grew  in  ages  long  gone  by,  pro- 
bably millions  of  years  ago.     The  plants  apparently  grew  principally 
in  clay  soils,  as  most  of  the  coals  are  underlaid  by  clay  of  various 
forms.     The  plants  died,  and  by  the  succeeding  operations  to  which 
the  earth's  crust  was  subject,  they  were  buried  by  overlying  strata, 
the  sites  where  they  had  grown  usually  being  submerged  after  the 
plants  had  died,  and  there  has  been  a  gradual  accretion  of  overlying 
strata  gradually   pushing  the   coal   seams   lower   and   lower  down 
beneath  the  surface.     The  coal  seams  occur  in  nearly  every  part  of 
the  world,  and  they  vary  in  thickness  from  a  very  few  inches  up  to 
as  much  as  ten  yards.     In  this  country  they  lie  in  basins,  spread  out 
so  that  the  edges  of  the  seams  come  out  to  the  surface  on  each  side 
of  the  basin,  and  the  seam  itself  is  inclined  to  the  vertical,  and  is 
found   at   lower  and  lower  depths  as  it  recedes  from   the  outcrop. 
In  other  parts  of  the  world — in  China,  for  instance — the  coal  seams 
are  stated  to  lie  in  large  basins,  almost  horizontal.     Volcanic  action 
has  been  very  busy  wherever  the  coal   seams  have   been   formed, 
has  disturbed  the  lay  of  the  strata,  and  in  addition  has  created  a 
considerable  amount  of  uncertainty  as  to  what  condition  the  coal 


40      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

will  be  found  in  when  it  is  reached,  in  different  parts  of  each  coal 
basin. 

Forms  of  Coal 

Coal  exists  in  very  variable  forms — brown  coal  or  lignite,  which 
is  found  in  very  large  quantities  in  Bohemia,  Italy,  and  other  parts 
of  the  world,  and  in  small  quantity  in  Devonshire ;  bituminous  or 
true  coals,  as  they  are  sometimes  called,  semi-bituminous,  or  semi- 
anthracites,  anthracite,  and  cannel. 

Peat,  though  it  is  taken  to  be  a  distinct  substance,  is  apparently 
the  early  form  of  coal.  It  is  formed  on  the  surface  in  marshy 
districts,  very  large  quantities  being  found  in  Ireland,  in  the  well- 
known  peat  bogs,  and  a  considerable  quantity  in  the  low-lying 
parts  of  Somersetshire  and  elsewhere.  Peat  is  formed  from  certain 
plants  which  die  down,  but  which  do  not  cease  to  grow  after  they 
have  ceased  to  furnish  vegetation  upon  the  surface.  At  the  same 
time,  fresh  plants  are  produced  at  the  surface  in  each  season,  which 
in  their  turn  die,  and  go  to  add  to  the  mass  of  peat  lying  below 
them,  with  the  result  that  the  lower  layers  are  subject  to  a  certain 
amount  of  pressure,  similar  to,  but  very  much  smaller  than  the 
pressure  to  which  the  coal  seams  have  been  subject,  and  the  nature 
of  the  lower  layers  is  gradually  altered,  the  colour  of  the  top  layers 
being  light  brown,  while  that  of  the  lowest  layers  will  be  nearly 
black.  And  while  the  top  layers  consist  of  the  tangled  roots  and 
stems  of  the  plants,  clearly  distinguished,  the  lower  layers  have  been 
pressed  into  a  more  or  less  compact  mass,  in  which  the  stems  and 
roots  of  the  plants  are  not  easily  distinguishable.  Peat  contains  a 
very  large  quantity  of  moisture,  and  the  process  of  getting  it  con- 
sists in  cutting  the  layers  into  square  portions,  and  stacking  them  up 
something  after  the  manner  of  haystacks,  but  with  air  spaces  between 
the  different  layers,  so  that  the  air  can  penetrate  and  carry  off  the 
moisture  in  the  same  manner  as  in  the  water-cooling  towers  that 
will  be  described  later  on.  Even  when  thoroughly  dried,  so  far  as 
it  can  be  in  this  manner,  peat  still  contains  a  large  percentage  of 
water  held  in  suspension  in  its  pores,  and  hence  its  value  as  a  fuel 
is  considerably  reduced,  since,  as  will  be  explained,  the  water  which 
is  present  in  the  pores  of  a  fuel,  takes  heat  from  that  liberated  by 
the  combustion  of  the  fuel,  to  convert  itself  into  steam,  and  as  all 
water  takes  in  the  neighbourhood  of  1200  heat  units  per  Ib.  to  raise 
its  temperature  to  boiling-point  and  convert  it  into  steam,  the  loss 
may  be  a  very  serious  one. 

The  composition  of  peat,  leaving  out  water,  which  may  be  as 
much  as  20  per  cent  after  air-drying,  ranges  from  54  to  61  per  cent, 
of  carbon,  5  to  7  per  cent,  of  hydrogen,  from  28  to  32  per  cent,  of 


INTRODUCTORY  41 

oxygen,  and  from  1J  to  2^  per  cent,  of  nitrogen,  and  from  2  to  10 
per  cent,  of  ash.  Ash  is  the  residue  of  incombustible  matter  that 
remains  after  the  fuel  is  burned.  It  consists  of  the  following  sub- 
stances :  silica  in  the  proportion  of  from  29  to  53  per  cent,  of  the 
total  amount  of  ash  present,  alumina  and  oxide  of  iron  in  the  pro- 
portion of  35  to  87  per  cent.,  and  lime  from  4  to  12  per  cent.,  with 
small  quantities  of  magnesia,  anhydrous  sulphuric  acid,  and  phos- 
phoric acid.  The  quantity  of  ash  in  different  coal  varies  from  3  up 
to  15  per  cent. 

Both  nitrogen  and  the  incombustible  ash  lower  the  calorific  value 
of  the  fuel,  because  neither  of  them  bring  any  additional  heat  to  the 
common  stock,  and  both  of  them  absorb  heat  while  the  process  of 
combustion  is  going  on,  to  raise  themselves  to  the  temperature  of 
the  remainder  of  the  burning  mass.  It  will  be  understood  that  in  a 
furnace,  or  wherever  fuel  is  in  process  of  combustion,  any  substance 
that  is  present  will  assume  the  temperature  of  the  remainder  of  the 
burning  mass,  if  and  as  far  as  it  is  able  to  do  so. 

The  coals,  commencing  with  peat,  appear  to  follow  a  regular 
gradation,  approximately  according  to  their  age,  and  the  pressure  to 
which  they  have  been  subjected  by  the  overlying  strata.  After  peat 
come  the  brown  coals  or  lignites,  in  which  the  carbon  ranges  from  46 
up  to  60  per  cent.,  the  volatile  matter  from  40  to  54  per  cent.,  the 
sulphur  from  0  to  3  per  cent.,  the  ash  from  1  to  12J  per  cent.,  and 
the  moisture  from  1  to  25  per  cent.  Xext  come  the  bituminous 
coals,  in  which  the  carbon  ranges  from  50  to  75  per  cent.,  the 
hydrogen  from  4  to  5^  per  cent.,  the  oxygen  from  3  to  20  per  cent. 

Xext  come  the  semi-bituminous,  or  as  they  are  sometimes  nailed, 
the  semi-anthracite  coals,  which  stand  between  the  bituminous  and 
the  pure  anthracites.  Striking  examples  of  these  coals  are  the  well- 
known  smokeless  steam  coals  of  South  Wales,  and  the  Pochahontas 
coals  of  Western  Virginia,  U.S.A.  In  these  coals  the  carbon  ranges 
from  75  to  90  per  cent.,  the  hydrogen  is  in  the  neighbourhood  of  5 
per  cent.,  and  the  oxygen  from  5  to  7  per  cent. 

In  the  pure  anthracite  coals,  the  carbon  ranges  from  90  to  98  per 
cent.,  hydrogen  and  oxygen  making  up  the  remainder. 


Cannel  Coal 

Cannel  coal  is  a  distinct  variety,  which  is  of  great  value  for 
making  gas,  as  it  contains  such  a  large  quantity  of  gaseous,  or  vola- 
tile matter.  It  is  of  great  value  commercially"  for  gas  making,  but 
is  not  much  employed  for  steam  raising.  The  cannel  coals  contain 
from  26  to  55  per  cent,  of  carbon,  and  from  42  to  64  per  cent,  of 
volatile  matter,  and  from  2  to  14  per  cent,  of  ash. 


42      STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Differences  between  the  Coals 

As  already  explained,  the  principal  difference  between  the  coals, 
so  far  as  steam  raising  is  concerned,  is  the  quantity  of  carbon  and 
hydrogen,  ash  and  moisture  they  contain  respectively.  But  there 
are  other  distinguishing  features.  Thus  bituminous  coals  are  so 
called  because  on  heating,  in  a  closed  vessel,  liquid  bituminous  sub- 
stances are  given  off.  The  bituminous  coals  are  very  largely  used 
for  raising  steam,  but  they  have  not  such  a  high  value  as  the  semi- 
bituminous  and  anthracite  coals.  The  bituminous  coals  also  con- 
tain considerable  quantities  of  volatile  matter  in  the  form  of  hydro- 
carbons, and  it  is  the  hydrocarbons  which  largely  go  to  make  smoke, 
and  which  are  therefore  wasted  when  they  appear  as  smoke.  As 
will  be  explained  later,  one  of  the  difficulties  of  the  boiler  maker  and 
the  boiler  attendant,  is  the  complete  combustion  of  the  volatile 
matter  in  some  of  the  coals,  notably  the  bituminous  variety.  Unless 
the  whole  of  the  volatile  matter  is  completely  burned,  completely 
oxidized,  it  passes  through  the  furnace  and  the  boiler  flues,  doing 
very  little  good  in  the  way  of  heating  the  water  and  the  steam,  and 
then  passes  out  into  the  atmosphere,  and  gives  rise  to  the  smoke  we 
are  familiar  with. 

In  the  semi-bituminous  coals  the  hydrocarbons,  so  largely  present 
in  the  bituminous  coals,  are  almost  absent,  and  hence  the  claim  for 
smokelessness  raised  by  South  Wales  coal-owners.  In  Nature's  labo- 
ratory, many  hundred  yards  below  the  surface  of  the  ground,  the 
vegetable  matter  of  the  plants  from  which  the  coal  is  formed  is 
gradually  changed,  the  hydrocarbons  being  apparently  first  separated 
from  the  carbon,  but  held  in  the  coal,  ready  to  give  way  with  a  slight 
application  of  heat,  and  at  a  further  stage  the  hydrocarbons  are 
decomposed,  the  percentage  of  carbon  being  increased,  and  the  gases 
which  are  found  in  such  large  quantities  in  semi-bituminous  and 
anthracite  coal  seams  are  formed,  and  are  held  under  very  consider- 
able pressure,  within  the  pores  of  the  coal,  ready  to  give  out  immedi- 
ately the  pressure  is  lowered. 

In  the  anthracite  variety  the  process  is  complete,  as  far  as  Nature 
is  able  to  carry  it,  and  the  coal  consists  almost  entirely  of  carbon, 
with  the  gases  mentioned  held  in  its  pores. 


Carbon  and  Volatile  Matter  in  Coals 

In  referring  to  the  different  qualities  of  coal  above,  the  term 
"volatile  matter"  was  used,  and  it  will  be  found  in  every  description 
of  coals  that  is  met  with.  The  meaning  is  as  follows.  There  are 


INTRODUCTORY  43 

three  methods  of  testing  the  calorific  value  of  any  fuel,  known 
respectively  as  proximate  analysis,  ultimate  analysis,  and  calori- 
metry.  In  the  proximate  analysis  a  small  quantity  of  the  fuel  is 
subjected  to  a  temperature  of  from  250°  to  300°  F.  to  expel  any 
moisture  that  may  be  present,  and  it  is  then  heated  to  redness,  the 
volatile  matter  being  driven  off  at  this  temperature.  After  the  vola- 
tile matter  has  been  expelled,  the  residue  is  further  heated  to  a  white 
heat,  at  which  temperature  the  carbon  present  combines  with  oxygen, 
and  passes  off  as  carbonic  acid.  The  residue  is  weighed  after  each 
operation.  The  percentage  of  the  original  sample  remaining  after 
heating  to  redness  is  given  as  a  percentage  of  carbon.  The  difference 
between  the  weight  of  the  sample  before  heating,  and  its  weight  after 
the  moisture  has  been  driven  off,  is  evidently  the  weight  of  moisture 
present.  The  difference  between  this  weight  and  that  after  heating 
to  redness  is  the  quantity  of  volatile  matter.  The  difference  between 
the  weight  remaining  after  heating  to  redness,  and  that  after  the 
carbon  has  all  been  oxidized,  is  the  weight  of  carbon,  and  the 
remainder  is  the  weight  of  ash.  It  is  usual  to  express  the  quantities 
as  percentages.  The  volatile  matters  are  the  hydrocarbons  mentioned 
above. 

In  ultimate  analysis  the  actual  percentages  of  carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur  of  ash  are  accurately  determined,  and  in 
estimating  the  heating  value  of  a  given  fuel,  it  is  these  quantities 
that  are  employed,  Dulong's  formula,  given  above,  being  employed. 


Calorimetry 

It  will  be  evident,  however,  that  neither  the  proximate  analysis 
nor  the  ultimate  analysis  can  give  an  accurate  estimate  of  the 
heating  value  of  a  fuel,  because  neither  of  them  show  how  the 
different  elements  are  combined  in  the  fuel,  and  their  combination  has 
a  most  important  bearing  upon  their  heating  value.  Combustion,  as 
explained,  is  a  chemical  operation,  and  nearly  all  chemical  operations 
in  which  heat  is  either  liberated  or  absorbed,  are  made  up  of  several 
subsidiary  operations,  some  of  which  liberate  heat,  and  some  of  which 
absorb  heat,  the  final  result  being  the  algebraical  sum  of  the  whole 
of  the  operations.  In  the  great  majority  of  cases,  when  two  sub- 
stances combine,  particularly  when  a  solid  combines  with  a  gas,  heat 
is  liberated ;  and,  on  the  other  hand,  when  a  compound  is  split  up 
into  its  components,  heat  is  absorbed.  As  the  different  elements 
contained  in  coal  may  be  present,  partly  in  combination  with  each 
other,  partly  in  the  free  state,  both  the  ultimate  and  proximate 
analyses  can  only  give  an  approximate  measurement  of  the  calorific 
value  of  the  fuel.  A  nearer  estimate  is  obtained  by  the  use  of  the 


44      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

calorimeter,  of  which  there  are  several  forms.  The  principle  of  the 
calorimeter  is  the  heating  of  a  definite  quantity  of  water  by  the  com- 
bustion of  a  definite  quantity  of  the  fuel  to  be  tested.  The  calorimeter 
consists  of  a  vessel  containing  a  definite  quantity  of  water.  In  I  one 
form  the  quantity  of  water  is  2  litres,  equal  to  3' 52  pints.  The  vessel 
containing  the  water  is  carefully  insulated  thermally,  from  the  ingress 
or  egress  of  heat,  and  a  smaller  vessel,  sometimes  called  a  cartridge, 
in  which  the  fuel  is  to  be  placed,  is  inserted  in  the  vessel  containing 
the  water.  The  fuel  is  ground  to  a  powder,  sufficiently  small  to  pass 
through  a  sieve  of  100  meshes  to  the  inch,  and  is  dried  before  being 
placed  in  the  cartridge.  A  thermometer  is  fixed  in  the  vessel  con- 
taining the  water,  its  stem  projecting  above,  so  that  its  indications 
can  be  read,  and  the  vessel  containing  the  fuel  is  also  arranged  on 
pivots,  so  that  it  can  be  rapidly  revolved.  Different  arrangements 
are  made  for  igniting  the  fuel  after  everything  is  ready.  The  fuel  is 
burned  under  the  conditions  named  above,  and  the  rise  of  temperature 
of  the  water  is  taken,  this  furnishing  a  definite  measurement  of  the 
heating  value  of  that  particular  fuel.  The  measured  results  by 
calorimeter,  and  the  calculated  results  from  Dulong's  formula,  do  not 
vary  to  any  great  extent,  if  care  is  taken  in  the  experiment.  From 
a  list  of  measurements  taken  with  W.  Thomson's  calorimeter,  as 
compared  with  the  calculated  values  from  the  ultimate  analysis  of 
different  English,  Welsh,  and  Scotch  coals,  the  differences  range 
from  0-3  per  cent,  up  to  10  per  cent.,  the  average  of  the  cases  taken 
being  a  difference  of  only  1  per  cent. 


Wood 

In  certain  parts  of  the  world,  notably  California,  large  portions  of 
Asia,  Africa,  and  South  America,  there  is  no  coal  available,  the  cost 
of  freight  from  the  nearest  coal  field  is  very  high,  and  consequently 
in  those  districts  where  wood  is  plentiful,  it  has  been  largely  used  as 
a  fuel  for  raising  steam.  As  will  be  seen  when  dealing  with  boilers, 
special  arrangements  are  necessary  for  burning  wood,  and  the  wood 
itself  has  not  the  same  calorific  value  as  any  of  the  forms  of  coal  that 
have  been  mentioned,  or  peat.  The  composition  of  wood  ranges  from 
48  to  50  per  cent,  of  carbon,  about  6  per  cent,  of  hydrogen,  from  39 
to  44  per  cent,  of  oxygen,  a  small  quantity  of  nitrogen,  and  from 
2  to  4  per  cent,  of  ash,  the  calorific  value  ranging  from  7800  B.  Th. 
units,  up  to  9000.  It  will  be  noticed  that  the  proportion  of  oxygen 
is  very  large,  so  that  the  hydrogen  present  is  practically  neutralized. 
Wood  contains  from  20  to  25  per  cent,  of  moisture,  even  when  it  is 
what  is  known  as  air  dried.  In  its  natural  condition  when  felled, 
the  moisture  present  ranges  from  30  to  50  per  cent,  by  weight,  this 


INTRODUCTORY  45 

amount  being  reduced  to  from  20  to  25  per  cent,  if  the  wood  is 
exposed  to  an  air  current  for  a  considerable  time.  The  large 
percentage  of  moisture  present  seriously  reduces  the  practical  heat- 
ing value  of  wood  as  a  fuel,  since  the  moisture  has  to  be  raised 
to  the  temperature  at  which  steam  is  formed,  and  has  also  to  be 
converted  into  steam  at  the  expense  of  the  heat  liberated  by  the 
combustion  of  the  remainder  of  the  components.  The  net  calorific 
value,  therefore,  of  air-dried  wood  will  not  exceed  6500  B.  Th.  units 
per  pound,  and  that  of  wood  when  first  felled  will  be  in  the  neighbour- 
hood only  of  4000  B.  Th.  units.  The  calorific  values  of  the  different 
woods  vary  very  little  among  themselves,  though  the  specific  gravity 
varies  very  considerably,  from  04  up  to  1-0.  Wood  is  sold  by  the 
cord  in  America,  and  by  what  is  known  as  string  measure  in  this 
country,  and  the  comparative  values  of  a  certain  quantity  of  wood 
will  vary  with  its  specific  gravity.  Thus  any  given  quantity  by 
measure  of  the  lighter  woods,  such  as  pine,  poplar,  chestnut,  sycamore, 
cedar,  etc.,  will  have  only  approximately  half  the  calorific  value  of  a 
similar  quantity  by  measure  of  the  heavier  woods  such  as  oak  and 
hickory,  while  beech  and  ash  will  have  about  three  parts  the  calorific 
value  for  the  same  quantity  by  measure. 


Spent  Tan,  Straw,  Bagasse,  Corn  Stalks,  and 
other  Organic  Refuse 

There  are  several  forms  of  fuel  that  are  employed  for  steam 
raising  that  are  the  refuse  from  different  industries,  such  as  tanning, 
wheat  and  barley  growing,  sugar  production,  cotton  growing,  and 
others.  All  of  them  are  organic  substances,  that  is  to  say,  they  all 
contain  carbon  and  hydrogen,  as  well  as  oxygen,  nitrogen,  and  ash. 

Spent  Tan  is  the  fibrous  portion  of  oak  bark  that  remains  after 
the  tan  itself  has  been  employed  in  the  tanning  industry.  When 
perfectly  dry  it  has  a  calorific  value  of  about  6000  B.  Th.  units  per 
pound,  but  it  usually  contains  about  30  per  cent,  of  moisture,  and  its 
calorific  value  thereby  reduced  to  about  4000  B.  Th.  units  per  pound. 

Straw. — The  average  composition  of  straw  is  as  follows  :  carbon 
36  per  cent.,  hydrogen  5  per  cent.,  oxygen  38  per  cent.,  ash  5  percent., 
a  small  quantity  of  nitrogen,  and  water  about  16  per  cent.  The 
calorific  value  is  in  the  neighbourhood  of  5000  B.  Th.  units  per 
pound  when  dry,  but  the  net  calorific  value  will  not  much  exceed 
4000  B.  Th.  units. 

Bagasse,  or  as  it  is  sometimes  called,  Megasse,  is  the  husk  of  the 
sugar  cane,  from  which  the  juice  has  been  extracted.  The  usual 
process  is,  the  canes  are  passed  between  rollers,  the  juice  being 
squeezed  out  of  them,  as  far  as  possible,  and  the  husk,  which  consists 


46      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

of  woody  fibre,  is  employed  for  raising  steam.  Bagasse  has  a  two- 
fold value  as  a  fuel.  The  woody  fibre  consists  of  carbon,  hydrogen, 
etc.,  like  the  other  substances  that  have  been  mentioned,  and  in 
addition,  it  is  impossible  with  the  methods  employed,  to  extract  all 
the  juice  of  the  sugar,  and  this  has  a  calorific  value  of  its  own. 
From  8  to  15  per  cent,  of  sugar  remains  in  the  bagasse  after  passing 
through  the  rolls,  and  its  composition  ranges  from  40  to  50  per  cent, 
of  woody  fibre,  from  7  to  9  per  cent,  of  sugar,  and  from  40  to  50  per 
cent,  of  moisture. 

The  calorific  value  of  the  woody  fibre  in  the  bagasse  is  in  the 
neighbourhood  of  8000  B.  Th.  units  per  pound  of  bagasse,  and  the 
calorific  value  of  sugar  and  molasses  is  approximately  7000  B.  Th. 
units  per  pound.  The  calorific  value  of  bagasse  therefore,  apart  from 
the  presence  of  moisture,  would  be  in  the  neighbourhood  of  7500  B.  Th. 
units  per  pound,  but  from  this  must  be  subtracted  the  heat  required 
by  the  moisture,  so  that  the;net  calorific  value  may  be  as  low  as  3750 
B.  Th.  units.  With  excessive  moisture,  as  where  careless  or  ineffi- 
cient milling  rules,  the  calorific  value  of  the  bagasse  will  vary 
proportionately. 

Cotton. — The  stalks  from  the  cotton  trees  have  a  calorific  value 
of  about  4000  B.  Th.  units  when  dry,  any  moisture  that  is  present 
reducing  the  value,  as  already  explained. 

In  America  corn  and  maize  have  also  been  used  as  fuel  in  the 
outlying  districts  where  these  substances  were  very  plentiful,  and 
other  fuel  was  not.  The  calorific  value  of  corn  is  in  the  neighbour- 
hood of  8000  B.  Th.  units. 

Sawdust,  dried  manure,  are  also  employed  as  fuel.  It  will  be 
understood  that  special  forms  of  furnace  are  required  for  burning 
these  substances,  in  order  that  the  proper  quantity  of  air  shall  be 
delivered  to  them. 

Liquid  Fuels 

Petroleum,  coal  tar,  water-gas  tar,  all  have  high  calorific  values, 
and  are  all  employed  for  burning  in  boiler  furnaces,  to  raise  steam. 
Petroleum  is  known  principally  as  the  substance  that  is  burned  in 
oil  lamps,  and  in  oil  engines,  and  in  the  form  of  a  distillate  in  the 
engines  employed  for  motor-cars.  It  is  found  in  the  liquid  form  in 
several  parts  of  the  world,  in  Eussia  and  America  principally,  and  it 
is  also  distilled  from  the  shales  that  are  found  in  Scotland  and  in 
other  parts.  The  origin  of  petroleum  is  in  dispute.  One  rather 
favourite  theory  is,  that  petroleum  has  been  formed  very  much  as 
coal  has,  but  from  marine  plants.  The  composition  of  petroleum  is 
similar  to  that  of  coal,  but  the  carbon  is  less  than  in  the  anthracite 
forms  of  coal,  while  the  hydrogen  is  very  much  greater,  and  the 


INTRODUCTORY  47 

oxygen  very  much  less.  The  composition  ranges  from  80  to  87 
per  cent,  of  carbon,  from  11*5  to  14  per  cent,  of  hydrogen,  and 
from  0  to  6  per  cent,  of  oxygen.  The  specific  gravity  ranges  from 
0-786  to  0-938,  and  the  calorific  value  from  18,000  to  22000  B. 
Th.  units  per  pound.  The  petroleum  which  is  found  in  the  liquid 
form  is  usually  reached  by  wells,  sunk  to  the  strata  in  which 
the  petroleum  is  found,  and  from  which  it  sometimes  has  to  be 
pumped,  and  sometimes  rises  to  the  surface  without  pumping,  owing 
to  the  pressure  to  which  it  is  subject,  just  as  water  rises  in  some 
artesian  wells.  The  oil  is  frequently  diluted  with  water,  and  when 
sold,  may  contain  any  quantity  from  1  to  50  per  cent.  At 
the  oil  wells,  proper  arrangements  are  made  for  separating  the  oil 
from  the  water,  and  best  petroleum  should  not  contain  more  than 
1  per  cent,  of  water.  The  same  remarks  that  have  been  made  with 
regard  to  the  presence  of  moisture  in  wood  and  other  fuels,  apply 
equally  to  liquid  fuels.  Any  water  that  is  present,  absorbs  heat 
approximately  in  the  ratio  of  1200  B.  Th.  units  for  every  pound  of  water. 

The  petroleums  are  divided  into  three  groups,  known  respectively 
as  the  paraffin,  asphalt,  and  olefine.  The  paraffin  group  are  dark 
brown  with  a  greenish  tinge,  and  the  oil  is  used  principally  for 
illumination.  The  asphalt  group,  found  in  California  and  Texas,  vary 
in  colour  from  reddish  brown  to  jet  black.  The  olefine  group  are 
found  principally  in  Eussia.  The  asphalt  and  olefine  groups  are  used 
principally  for  fuel. 

A  gallon  of  petroleum  weighs  in  the  neighbourhood  of  6-J  Ibs., 
the  weight  varying  with  the  specific  gravity  of  the  substance."  The 
petroleum,  as  it  comes  from  the  wells,  is  subject  to  a  process  of  dis- 
tillation, partly  for  the  purpose  of  removing  foreign  matters,  and 
partly  to  separate  the  various  oils  that  are  contained  in  the  petroleum, 
and  that  are  used  for  illuminating  and  other  purposes,  such  as  gasoline, 
benzine,  and  kerosene.  These  substances  are  formed  into  vapour  at 
different%temperatures,  and  hence  can  be  separated  from  each  other, 
and  from  the  parent  substance,  by  what  is  called  fractional  distilla- 
tion, the  different  vapours,  as  they  come  away,  being  condensed  in 
different  vessels.  It  is  the  residuum,  the  substance  remaining  after 
the  illuminating  and  other  oils  have  been  carried  over,  that  is  used 
for  fuel ;  it  is  known  sometimes  as  petroleum  refuse. 


Flash  Point  and   Ignition  Point 

There  are  two  very  important  matters  in  connection  with  the 
handling  of  liquid  fuels,  the  temperature  at  which  the  oil  or  fuel 
gives  off  an  inflammable  gas,  and  the  temperature  at  which  it 
ignites.  The  temperature  at  which  an  inflammable  gas  is  given  off 


48       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

is  known  as  the  flash  point,  and  the  flash  point  is  lower  with  the 
lighter  oils — those  whose  specific  gravity  is  low,  and  whose  illumi- 
nating value  is  comparatively  high — than  with  the  oils  and  refuse  of 
higher  specific  gravity. 

The  process  of  obtaining  oil  from  the  shales  mentioned  above,  is 
very  similar  to  that  employed  in  separating  the  different  oils  found 
in  the  liquid  petroleum.  Shale  is  a  substance  somewhat  similar  in 
appearance  to  cannel  coal.  It  is  a  solid,  and  it  is  distilled  in  ver- 
tical retorts,  the  products  of  distillation,  the  vapours  which  are 
formed,  being  condensed  in  the  same  manner  as  those  from  the 
liquid  petroleum,  and  these  being  valuable  for  illuminating  oils  and 
for  fuel. 


Gas  Tar  as  Fuel 

Another  substance  that  is  occasionally  employed  as  fuel,  is  the 
tar  that  is  a  by-product  in  the  generation  of  illuminating  and  other 
gases.  When  coal  is  distilled  in  the  gas  retorts  for  the  production 
of  illuminating  gas,  in  addition  to  the  gas  itself,  a  product  comes 
away,  known  generically  as  tar,  from  which  the  aniline  dyes  and 
other  substances  are  afterwards  produced.  The  tar  is  of  too  high  a 
commercial  value  to  be  used  as  fuel,. but  it  has  its  own  calorific  value, 
which  is  found  from  its  composition.  It  contains  approximately  89 
per  cent,  of  carbon,  5  per  cent,  of  hydrogen,  4  per  cent,  of  oxygen, 
|-  per  cent,  of  sulphur,  and  a  minute  quantity  of  ash,  and  its  calorific 
value  is  given  as  in  the  neighbourhood  of  15,000  B.  Th.  units.  Tar 
is  also  produced  in  the  process  of  generation  of  the  various  producer 
gases,  water  gas,  and  others,  and  it  is  also  present  in  blast  furnace 
and  coke  oven  gases.  The  tar  is  carefully  separated  from  the  illumi- 
nating gas  before  it  is  allowed  to  pass  into  the  gas-holders  for 
distribution  to  consumers,  and  the  apparatus  for  its  separation  and 
for  the  purification  of  the  gas  forms  a  large  portion  of  the  plant  at  a 
modern  gas  works.  Similarly  the  gas  produced  from  gas  producers  is 
also  separated  from  any  tarry  and  other  products  that  may  be  present, 
and  for  the  reason  that  the  gas  engines  in  which  producer  and  other 
gases  are  employed  would  soon  have  the  working  of  their  valves  and 
cylinders  seriously  interfered  with,  if  the  tar  was  allowed  to  remain 
in  the  gas,  as  it  would  be  deposited  in  valve  passages  on  the  inside 
of  cylinders,  and  so  on.  The  tar  from  gas  producers  and  coke  ovens, 
etc.,  has  a  slightly  different  position  to  that  formed  from  illuminating 
gas,  carbon  being  about  92  per  cent.,  hydrogen  6  per  cent.,  nitrogen  O'l 
per  cent.,  oxygen  0'7  per  cent.,  sulphur  0*3  per  cent.,  and  a  minute 
quantity  of  ash.  The  calorific  value  is  given  as  about  17,000  B.  Th. 
units. 


PLATE   IA. — Galloway  Cornish  boiler,  with  cone  tubes.     The  single  central  inside 
;.'flue  and  the  outside  brickwork  flues  are  shown. 


PLATE  IB. — Battery  of  Lancashire  boilers,  by  Messrs.  Huston,  Proctor  &  Co. 

[To  face  p.  48. 


INTRODUCTORY  49 


Burning  Liquid  Fuels 

Special  arrangements  are  necessary  to  enable  liquid  fuels  to  be 
burned,  whether  in  the  furnace  of  a  boiler,  or  in  the  cylinder  of  an 
internal  combustion  engine.  It  is  really  the  vapour  which  comes 
away  from  the  surface  of  any  oil,  that  is  used  either  for  heating  or 
illuminating  purposes,  that  is  burned.  It  is  not  the  oil  itself,  until 
it  has  been  converted  into  vapour,  and  the  apparatus  required  for 
enabling  liquid  fuel  to  be  burned  consists  of  arrangements  for  either 
breaking  it  up,  or  raising  its  temperature,  so  that  it  becomes  vapour. 
Broadly,  there  are  two  methods  of  handling  liquid  fuel — by  breaking 
it  up  into  a  very  fine  spray,  and  in  that  form  mixing  it  with  the  air, 
each  particle  of  the  liquid  seizing  upon  the  quantity  of  oxygen  it 
requires  from  the  atmosphere  surrounding  it;  and  by  raising  the 
temperature  of  a  certain  portion  of  it  to  that  at  which  it  gives  off 
vapour,  the  vapour  as  it  comes  away  passing  into  a  current  of  air. 

The  different  methods  employed  will  be  described  in  connection 
with  the  boiler  furnaces.  It  will  be  sufficient  to  mention  here  that 
all  liquid  fuels,  oils  and  refuse  of  oils,  and  tars,  require  to  be  handled 
in  this  way. 

Gaseous  Fuel 

There  are  several  forms  of  gaseous  fuel  employed  for  firing  boilers. 
Ordinary  illuminating  gas  may  be  employed  for  the  purpose,  if  it  is 
convenient  in  other  ways,  but  it  is  usually  more  economical  to  burn 
it  in  the  cylinder  of  an  internal  combustion  engine.  It  should  be 
mentioned  incidentally  that  this  remark  applies  to  all  gaseous  fuels, 
but  as  the  object  of  this  book  is  to  show  all  possible  methods  of 
generating  steam,  and  utilizing  it  for  power,  the  gaseous  fuels  used 
in  boiler  furnaces  must  be  dealt  with. 

In  addition  to  the  ordinary  illuminating  gas,  there  are  the  pro- 
ducer gas  referred  to  below,  blast-furnace  gas,  coke-oven  gas,  and 
what  is  termed  natural  gas. 


Producer  Gas 

The  producer  gases  are  all  made  on  somewhat  the  same  lines. 
Either  steam,  or  steam  and  air,  are  forced  through  a  mass  of  incan- 
descent fuel,  preferably  anthracite  coal  or  coke,  though  bituminous 
coals  are  also  employed  for  the  purpose.  The  high  temperature  at 
which  the  fuel  is  maintained  decomposes  the  water  into  its  con- 
stituents, oxygen  and  hydrogen,  the  carbon  of  the  fuel  combining 


50      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

with  both  of  them,  and  with  the  oxygen  of  the  atmosphere,  if  the 
air  is  employed  as  well,  the  result  being  the  formation  of  a  gas 
largely  consisting  of  carbonic  oxide.  The  composition  of  producer 
gas  varies  with  the  different  methods  of  production,  but  it  will  be 
approximately  as  follows:  carbonic  oxide  24  per  cent.,  hydrogen 
8  per  cent.,  carburetted  hydrogen  2  per  cent.,  carbonic  acid  4  per  cent., 
nitrogen  61  per  cent.,  and  a  small  quantity  of  oxygen.  It  is  usual 
to  express  the  calorific  value  of  gaseous  fuel  in  terms  per  cubic  foot 
of  the  gas.  The  calorific  value  of  producer  gas  ranges  from  120  to 
200  B.  Th.  units  per  cubic  foot. 

The  gas  produced  by  suction  gas  producers  is  not  intended  to 
be  used  with  boiler  firing,  and  cannot  be  employed  unless  special 
arrangements  are  made  to  imitate  the  sucking  action  of  the  internal 
combustion  engines. 

Blast  Furnace  Gas 

Blast  furnace  gas  is  formed  in  the  process  of  smelting  iron. 
What  is  known  as  pig  iron,  from  which  wrought  iron,  steel,  etc., 
is  afterwards  made,  is  produced  in  the  blast  furnace,  a  large  structure 
nearly  cylindrical,  its  internal  section  being  partly  that  of  an  inverted 
cone,  and  having  a  grate  on  the  bottom  of  the  cone,  on  which  a  fire  is 
lighted.  The  furnace  is  fed  with  the  iron  ore  to  be  smelted,  which 
consists  largely  of  iron  and  oxygen.  A  quantity  of  limestone  is 
employed  as  a  flux  to  enable  the  smelted  iron  to  run  freely,  and  a 
quantity  of  coke,  whose  combustion  supplies  the  heat  necessary  for 
the  melting  of  the  iron  and  its  separation  from  the  oxygen  and 
impurities.  A  powerful  current  of  air  is  constantly  forced  through 
the  furnace  by  means  of  powerful  engines,  the  current  of  air  being 
known  as  the  blast,  and  hence  the  furnace  being  called  a  blast 
furnace.  The  carbon  in  the  coke  unites  with  the  oxygen  of  the  air 
in  the  blast,  and  also  with  some  of  the  oxygen  which  is  driven  off 
from  the  iron  ore,  the  result  being  the  formation  of  a  gas  containing 
a  large  quantity  of  carbonic  oxide,  the  gas  coming  away  from  the  top 
of  the  furnace.  A  portion  of  the  gas  is  employed  in  heating  the  air 
which  is  driven  into  the  furnace,  usually  about  half  the  total  quantity 
of  gas  delivered  by  the  furnace,  but  the  remainder  is  available  for 
use  either  in  internal  combustion  engines,  or  for  combustion  in  the 
furnaces  of  steam  boilers.  It  is  employed  very  largely  at  iron  works 
for  raising  steam  to  drive  the  blast  engine,  though  in  later  practice 
the  blast  engine  is  an  internal  combustion  engine,  and  the  gas  is  con- 
sumed in  its  cylinder.  There  is  usually  some  gas  remaining  after  the 
heating  stoves  for  the  blast  and  the  requirements  of  the  blast  engine 
have  been  satisfied,  that  can  be  employed,  if  desired,  for  raising 
steam.  The  composition  of  blast  furnace  gas  varies  again,  carbonic 


INTRODUCTORY  51 

oxide  being  the  important  constituent,  and  the  one  upon  which  the 
heating  value  of  the  gas  as  a  fuel  depends.  The  composition  is  as 
follows  :  carbonic  oxide,  from  24  to  34  per  cent. ;  carbonic  acid, 
from  1  to  12  per  cent. ;  nitrogen,  from  57  to  64  per  cent. ;  hydrogen, 
from  0  to  5  per  cent. ;  hydrocarbons,  from  1  per  cent,  downwards. 
Its  calorific  value  is  from  120  to  150  B.  Th.  units  per  foot. 


Coke-oven  Gas 

Coke  is  made  very  largely  at  collieries  where  coking  coals  are  pro- 
duced, the  process  being  very  similar  in  many  respects  to  that  for 
producing  ordinary  illuminating  gas.  The  coke  is  produced  in  coke 
ovens  of  various  forms,  from  small  coal  that  has  been  previously 
washed  to  cleanse  it  from  ash,  sulphur,  and  other  impurities.  The 
oven  is  filled  with  the  small  coal  and  then  closed  up,  the  mass 
being  then  heated,  either  by  some  of  the  gas  produced  from  the  coke 
itself  passing  through  channels  provided  for  it  surrounding  the  oven, 
or  by  the  heat  liberated  by  the  burning  of  the  coal  itself  in  the  oven. 
In  either  case  the  production  of  the  coke  consists  in  driving  off  the 
volatile  matter,  the  gases  that  are  present  in  the  coal,  leaving  a  mass 
of  nearly  pure  carbon.  In  the  older  forms  of  coke  ovens,  some  of 
which  may  still  be  seen  in  various  parts  of  the  kingdom,  and  may  be 
known  by  the  flames  they  emit  from  the  tops  of  the  furnaces,  the  gas 
was  allowed  to  pass  away  into  the  atmosphere.  In  the  modern  form 
of  coke  oven  part  of  the  gas  is  employed,  as  explained  above,  in  heat- 
ing the  oven,  and  the  remainder,  usually  about  half  that  generated, 
is  available  for  use  in  the  furnaces  of  boilers  or  in  the  cylinders  of 
internal  combustion  engines,  or  wherever  heat  is  required.  The 
calorific  value  of  coke-oven  gas  is  about  400  B.  Th.  units  per 
cubic  foot. 

Natural  Gas 

By  natural  gas  is  understood  the  gas  that  is  found  free  in  the 
ground,  not  much  in  this  country,  but  well  known  and  largely  used 
in  America,  and  that  has  been  produced  by  natural  forces,  very  much 
in  the  same  manner  as  coal  and  petroleum  have  been  produced. 
Possibly  the  natural  gas  may  be  emanations  from  the  coal  in 
process  of  natural  distillation.  In  America  natural  gas  is  found 
at  various  depths  below  the  surface,  is  pumped  from  wells  to  the 
points  where  it  is  to  be  employed,  and  is  used  there  in  the  same 
manner  as  ordinary  illuminating  gas  would  be  employed.  Its 
composition  varies  with  the  locality,  and  its  calorific  value  necessarily 
varies  with  its  composition.  One  composition  given  is  as  follows : 


52       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

marsh  gas,  CH4,  which  is  the  gas  found  in  coal  mines,  72 '15  per  cent. ; 
olefiant  gas,  C2H4,  which  is  one  of  the  principal  gases  in  ordinary 
illuminating  gas,  0*66  per  cent.  ;  ethane,  another  gas  of  the  same 
series,  C2H6,  4  per  cent. ;  carbonic  oxide,  1  per  cent. ;  carbonic  acid, 
0'3  per  cent. ;  oxygen,  0'4  per  cent.  Its  calorific  value  is  given  as 
over  900  B.  Th.  units  per  cubic  foot. 


The  Oases  found  in  Collieries 

There  is  another  source  of  fuel  that  at  present  is  both  a  nuisance 
and  a  danger,  but  which  in  time  to  come  will  probably  be 
employed  as  a  source  of  power,  viz.  the  gas  which  is  found  in  the 
coal  measures,  and  which  has  been  produced  by  the  distillation  of 
the  organic  substances  contained  in  the  plants  from  which  the  coal 
was  formed,  during  the  ages  since  the  plants  were  buried.  The  gas 
consists  almost  entirely  of  that  known  as  marsh  gas,  having  the 
chemical  formula  CH4.  It  is  largely  imprisoned  in  the  pores  of  the 
coal  itself,  it  is  thought  in  the  liquid,  and  possibly  even  in  the  solid, 
form,  and  under  very  great  pressure,  with  the  result  that  it  comes 
away  freely  as  the  coal  is  worked  and  the  pressure  to  which  it  is 
subject  is  reduced.  One  great  reservoir  of  this  form  of  natural  gas  is 
found  in  the  coal  fields  of  South  Wales  in  the  faults  in  the  strata. 
It  was  explained,  in  dealing  with  the  production  of  coal,  that  the  coal 
seams  or  coal  measures  had  been  subject  to  great  disturbing  influences 
from  upheavals  of  the  strata,  from  the  same  causes  that  produce  earth- 
quakes and  the  eruptions  of  volcanos.  The  result  has  been  that  the 
strata  has  been  broken  and  that  the  edges  of  the  coal  seams  have  been 
presented  to  the  edges  of  other  rocks,  a  very  fine  capillary  space 
being  present  between  them,  and  in  this  space  the  gas  from  the  coal 
seam  is  apparently  stored.  On  several  of  the  colliery  pit  banks  in 
South  Wales  may  be  seen  jets  of  gas  burning  day  and  night,  some- 
thing on  the  lines  of  the  flares  that  butchers  favour  on  their  stalls  on 
Saturday  nights,  the  gas  issuing  from  the  end  of  a  pipe.  These 
flames  are  produced  by  the  gas  carried  by  means  of  these  pipes  from 
the  faults  mentioned  above,  and  it  is  merely  a  step  from  burning 
them  wastefully,  to  storing  them  and  using  them  for  power.  In  one 
colliery  in  South  Wales  they  have  been  used  for  some  time,  after 
scrubbing,  for  illuminating  purposes. 


CHAPTER  II 

BOILERS 
The  Steam  Boiler 

THE  steam  boiler  is  an  apparatus  designed  for  the  conversion  of  water 
into  steam  by  the  aid  of  heat  liberated  by  the  combustion  of  one 
of  the  fuels  that  have  been  enumerated  in  the  previous  chapter. 
It  is  made  in  a  very  large  variety  of  forms,  all  designed  with  the  view 
of  increasing  its  efficiency,  or  increasing  the  real  efficiency  of  the 
steam  plant  as  a  whole,  by  decreasing  the  repairs  and  the  attendants' 
bill.  All  of  them  must  contain  a  space  in  which  water  is  carried, 
and  to  which  a  continuous  supply  of  water  can  be  added  as  that 
present  is  converted  into  steam.  They  must  also  contain  a  space  in 
which  the  steam  that  is  generated  can  be  stored  until  it  is  drawn 
away  to  the  engines  or  turbines  that  use  it.  They  must  also  have 
some  arrangement  for  the  burning  of  the  fuel  that  is  to  be  em- 
ployed as  the  source  of  heat.  The  question  of  economical  con- 
sumption of  the  fuel,  and  of  the  utilization  of  the  largest  proportion 
of  the  heat  liberated  by  the  combustion  of  the  fuel,  is  responsible  for 
the  principal  designs  of  the  various  boilers.  When  we  examine  the 
question  of  the  combustion  of  any  fuel — say,  for  example,  that  of  coal 
in  our  domestic  grates — we  find  that  it  is  exceedingly  wasteful.  As 
explained  in  the  first  chapter,  heat  is  liberated  by  the  combination, 
principally  of  the  carbon  and  hydrogen  in  the  fuel,  with  the  oxygen 
of  the  atmosphere  that  is  supplied  to  the  fuel,  the  mass  of  fuel  and 
the  air  supplied  to  it  being  converted  nearly  all  into  gas,  the  more 
nearly  the  whole  can  be  converted  into  gas  the  more  economical  being 
the  process  of  combustion,  and  the  more  easily  the  furnaces  in  which 
the  fuel  is  burned  being  worked.  But  it  follows  that  the  heat 
liberated  by  the  burning  fuel  is  almost  entirely  delivered  to  the 
gases  that  are  formed  from  it  and  those  of  the  air  that  are  present 
but  are  not  in  combination ;  and  in  the  case  of  the  domestic  fire- 
grate, as  these  gases  pass  directly  up  the  chimney,  the  major  portion 
of  the  heat  liberated  passes  there  also,  only  a  small  quantity  of  the 

53 


54      STEAM   BOILERS,   ENGINES,  AND   TURBINES 

total  heat  passing  out  into  the  room,  by  radiation  from  the  glowing 
coals,  or  from  the  flames  that  are  produced  as  the  coal  burns.  The 
enormous  waste  involved  in  the  burning  of  coal  in  the  ordinary  fire- 
grate will  be  appreciated  when  it  is  pointed  out  that  the  combustion 
of  1  oz.  of  coal,  measuring  about  2  cubic  inches,  should  be  sufficient 
to  raise  half  a  gallon  of  water  to  boiling-point  or  to  raise  the 
temperature  of  the  air  of  a  room  of  4000  cubic  feet  10°  F.  We  know 
perfectly  well  from  our  experience  that  the  combustion  of  the  ounce 
of  coal,  consisting  of  a  small  knob  that  we  throw  on  the  fire,  will  do 
nothing  of  the  kind,  and  the  reason  is  as  stated  above.  In  early 
forms  of  boilers  something  of  the  same  kind  of  waste  took  place,  but 
successive  advances  have  been  made,  the  object  of  all  of  which  has 
been  to  utilize,  as  far  as  possible,  the  whole  of  the  heat  delivered  to 
the  gases.  For  this  purpose  the  hot  gases  are  not  allowed  to  pass 
immediately  to  the  chimney,  but  are  taken  to  it,  in  all  forms  of  boiler, 
by  a  more  or  less  circuitous  path,  in  the  course  of  which  they  pass 
over  metal  surfaces,  on  the  other  side  of  which  are  placed  bodies  of 
water,  to  which  the  heat  is  transmitted,  and  from  which  steam  is 
formed. 

Circulation  in  Boilers 

Another  important  matter  in  connection  with  the  heating  of 
water,  is  that  of  the  circulation  of  the  water  within  the  boiler.  It 
was  pointed  out  in  the  first  chapter,  that  when  liquids  or  gases  are 
heated  they  expand,  a  given  volume  in  contact  with  the  heating 
surface,  becoming  lighter  than  the  surrounding  equivalent  volumes, 
is  pushed  away  from  the  heating  surface,  other  portions  of  the  liquid 
or  the  gas  taking  their  places,  and  convection  currents,  as  they  are 
called,  being  thereby  set  up,  enabling  the  mass  of  water  or  gas  to  be 
heated  all  over.  In  addition,  it  may  be  pointed  out  that  when  water 
is  in  contact  with  a  metallic  surface,  on  the  other  side  of  which  is  a 
source  of  heat,  minute  globules  are  formed  on  the  heated  surface, 
which,  unless  they  are  enabled  to  get  away  by  the  action  of  the 
convection  currents  mentioned,  resist  the  passage  of  the  heat  from 
the  metallic  surface  to  the  water  beyond  them.  Hence  it  is  of  great 
importance  that  the  water  in  a  boiler  should  be  kept  continually  in 
motion,  and  this  requirement  has  caused  the  development  of  some  of 
the  designs  of  boilers  that  will  be  described.  One  point  that  had 
better  be  mentioned,  as  it  is  a  very  striking  one,  is  that  if  heat  is 
delivered  to  the  whole  body  of  the  water,  or  to  the  upper  portions, 
very  little  circulation  takes  place,  and  water  being  a  poor  conductor 
of  heat  when  not  assisted  by  convection  currents,  the  heat  does  not 
easily  reach  the  lower  portions  of  the  mass  of  water,  and  any  arrange- 
ment of  the  kind  must  necessarily  be  very  wasteful.  This  applies, 


BOILERS  55 

to  a  smaller  extent,  to  heat  applied  to  the  sides  of  a  mass  of  water. 
The  best  position  for  any  source  of  heat  applied  to  raising  steam 
from  water,  is  on  the  lower  part  of  the  body  of  water.  The  domestic 
tea  kettle  is  the  most  striking  instance  of  this.  On  the  other  hand, 
as  will  be  explained,  the  structural  requirements  of  the  vessel,  or 
groups  of  vessels,  of  which  boilers  are  constructed,  require  the 
presence  of  water  in  certain  parts  of  the  boiler,  where  circulation 
is  not  easy.  Instances  of  this  are,  the  lower  part  of  the  Lancashire 
boiler  below  the  furnace,  and  the  back  of  the  marine  boiler,  as 
used  on  board  ship.  These  points  will  be  explained  more  fully 
when  describing  the  different  boilers,  but  it  may  be  mentioned 
here,  that  one  of  the  most  important  matters  in  connection  with 
the  construction  of  a  steam  boiler,  is  to  arrange  for  the  expan- 
sions and  contractions  that  take  place  in  the  metals  of  which  the 
boiler  is  composed,  the  expansions  being  very  great  with  the  very 
high  temperatures  present  in  some  parts  of  the  boiler,  and  also  to 
provide  for  the  differences  in  expansion  of  different  parts  of  the 
boiler,  owing  to  the  different  temperatures  to  which  they  are  exposed. 
Another  important  point  in  all  boilers,  is  to  ensure  that  water  shall 
be  present  on  the  opposite  sides  of  the  surfaces  that  are  exposed  to 
the  highest  temperatures. 


Fire=tube  Boilers 

The  earliest  forms  of  boiler  used  in  modern  times  were  those 
now  known  as  fire-tube,  to  distinguish  them  from  the  water-tube 
boilers  that  have  come  so  largely  into  use  during  recent  years.  Fire- 
tube  boilers  may  be  divided  into  Cornish  boilers,  Lancashire  boilers, 
and  multitubular  boilers,  each  of  these  forms  being  designed  with  the 
object  of  providing  a  path  for  the  hot  gases  through  them,  of  such 
a  nature  that  the  heat  can  be  easily  extracted  from  the  gases,  and 
delivered  to  the  water,  on  their  way  to  the  chimney.  The  Cornish  and 
Lancashire  boilers  are  very  similar  in  construction  up  to  a  certain  point. 
In  each  there  is  a  cylindrical  shell  forming  a  receptacle  for  the  water 
and  the  steam.  In  the  Cornish  boiler  a  portion  of  the  cylinder  is 
taken  for  the  provision  of  the  space  required  for  the  furnace,  and  for 
the  flue  through  which  the  furnace  gases  are  to  pass  on  their  way  to 
the  chimney,  and  through  which  they  are  to  deliver  their  heat  to  the 
water  in  the  boiler.  In  the  Lancashire  boiler  there  are  two  such  spaces 
taken  out  of  the  cylindrical  vessel,  for  two  furnaces  and  two  flues. 
In  both  the  Cornish  and  Lancashire  boilers  the  spaces  taken  for  the 
furnaces  and  flues  are  cylindrical,  that  for  the  Cornish  boiler  in  the 
earlier  forms  being  roughly  double  that  of  one  of  the  Lancashire. 
In  both  forms  of  boilers  the  cylinders  forming  the  flues  have  the 


56      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

furnaces  consisting  of  grate  bars  of  various  forms,  fixed  at  one  end, 
the  grate  bars  being  placed  a  little  above  the  middle  of  the  flue 
cylinder,  and  sloping  slightly  towards  the  other  end,  as  shown  in 
Fig.  5.  At  the  end  of  the  grate  bars  a  fire-brick  bridge  is  usually 
built,  as  shown  in  the  figure,  which  becomes  white  hot  from  the 
passage  of  the  hot  gases  over  it,  and  assists  in  ensuring  the  com- 
plete combustion  of  the  fuel.  The  hot  gases  formed  by  the  combustion 
of  the  fuel  and  the  air  with  which  it  combines,  pass  from  the  fire- 
grate over  the  bridge  and  through  the  flues  in  both  the  Cornish  and 
Lancashire  boilers,  to  the  opposite  end  of  the  boiler,  and  from  there  are 


FIG.  5. — Sectional  Drawing  of  internally  fired  "Cornish"  and  Multitubular  Boiler, 
made  by  Messrs.  Marshall.  The  Hot  Gases  pass  from  the  Central  Boiler  Flue 
through  the  Tubes  at  the  back,  thence  through  the  Under  and  Side  Flues  to  the 
Chimney.  A  Section  of  the  Furnace  is  shown,  at  the  front  of  the  Boiler,  and  it 
will  be  noticed  how  the  Fire-bars  slope  inwards  towards  the  Bridge. 

usually  brought  under  the  lower  surface  of  the  boiler  to  the  furnace 
end,  and  when  a  little  way  from  the  front  are  divided,  half  of  the 
gases  passing  on  each  side  of  the  outer  shell  of  the  boiler  to  the  back 
end  again,  where  they  pass  to  the  chimney.  As  shown  in  Figs.  5 
and  6,  and  Plates  2A,  2B,  and  2c,  fire-brick  flues  are  built  round 
the  outside  of  both  Cornish  and  Lancashire  boilers,  the  boiler 
shells  being  held  between  the  edges  of  a  row  of  fire  bricks,  and 
the  remainder  of  the  bricks  being  arranged  to  provide  the  external 
flues,  through  which  the  hot  gases  pass  as  described.  In  both 
Lancashire  and  Cornish  boilers,  it  will  be  seen  the  hot  gases  pass 
three  times  from  end  to  end  of  the  boiler,  from  the  furnace  to 


BOILERS 


57 


58      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  back  end,  from  the  back  end  to  the  front  end  under  the 
boiler,  and  from  the  front  end  to  the  back  end  again  by  way  of 
the  side  flues.  It  will  be  understood  that  the  cylindrical  vessels 
forming  both  the  Cornish  and  Lancashire  boilers,  contain  water 
up  to  a  certain  level,  usually  several  inches  above  the  tops  of  the 
flues,  this  being  a  very  important  point.  The  crowns  of  the  furnaces 
in  particular,  as  the  upper  portion  of  the  cylinders  forming  the 
furnaces  and  flues  are  called,  should  always  have  a  substantial 
quantity  of  water  lying  on  them,  so  that  the  crowns  themselves 
should  not  reach  a  dangerous  temperature.  The  water  lying  on  the 
furnace  crowns  carries  off  the  heat  as  it  is  delivered  to  the  furnace. 
Water  lies  all  round  the  cylindrical  flues,  and  it  lies  on  the  inside 
of  the  boiler  where  the  bottom  and  side  flues  are  built,  and  therefore 
the  hot  gases  passing  through  the  outside  flues  are  able  to  transmit 
the  heat  they  possess,  through  the  outer  metal  surfaces  to  the  water 
on  the  inside. 

It  will  be  noticed  from  the  above,  and  it  will  be  seen  more  clearly 
from  the  Figs,  and  Plates  mentioned,  that  there  is  one  part  of  the 
cylinders  of  both  Cornish  and  Lancashire  boilers  over  which  the  hot 
gases  do  not  pass,  viz.  the  segment  forming  the  upper  portion.  It  is 
that  portion  in  which  the  steam  generated  is  contained,  and  it  is  a 
rule  in  boiler  construction,  and  boiler  working,  that  the  steam  space 
is  not  to  be  exposed  to  the  hot  gases,  and  vessels  containing  steam 
are  not  to  be  exposed  to  heat,  except  in  the  case  of  the  special 
arrangements,  described  later,  for  superheating  the  steam.  This 
upper  portion  of  the  boiler  should  be  covered  with  a  thermal  insu- 
lators, so  that  the  heat  present  in  the  steam,  which  is  communicated 
to  the  boiler  shell,  should  not  be  lost  by  radiation,  as  it  is  if  no 
protection  is  provided  for  it.  The  importance  of  covering  this  space 
with  a  thermal  insulator,  and  of  covering  steam  pipes,  as  will  be 
explained  later,  will  be  seen  from  the  fact  that  each  square  foot  of 
boiler  or  pipe  surface  radiates  when  unprotected  by  thermal  insulators, 
2*812  B.  Th.  units  per  hour,  for  every  degree  difference  of  tempera- 
ture between  itself  and  the  temperature  of  the  surrounding  atmo- 
sphere (Siebel).  Taking  the  temperature  of  the  atmosphere  in  this 
country  as  averaging  60°  F.,  with  steam  of  150  Ibs.  gauge  pressure, 
this  would  mean  a  radiation  of  300  times,  2*812  B.  Th.  units  for 
each  square  foot  of  surface  exposed ;  or,  again,  taking  the  case  of  a 
Lancashire  boiler  8  feet  in  diameter,  and  30  feet  long,  the  area  exposed 
to  radiation  would  be  about  200  square  feet,  and  this  would  mean,  with 
average  temperatures,  a  loss  by  radiation  of  168,720  B.  Th.  units  per 
hour,  and  with  some  winter  temperatures,  of  much  more.  From  Fig.  5, 
it  will  be  seen  that  in  the  water  lying  on  top  of  the  furnace  crowns 
receives  the  largest  amount  of  heat,  that  lying  on  top  of  the  flues 
beyond  receiving  the  next  largest,  that  by  the  side  of  the  furnaces 


BOILERS  59 

and  'flues  the  next,  while  the  remainder  of  the  water  in  the  boiler 
receives  gradually  less  and  less  heat,  as  the  temperature  of  the  gases 
passing  over  the  metal  separating  it  from  them  decreases.  It  will 
be  noticed  also  that  portions  of  the  water  in  the  boiler  are  placed 
between  two  heating  surfaces,  that  at  the  sides  and  between  the 
flues  and  furnaces.  But  while  the  water  at  the  bottom  of  the  boiler 
is  also  between  the  bottom  of  the  flues  and  the  lower  surface  of  the 
boiler,  and  is  exposed  to  the  hot  gases  as  they  pass  from  the  back  of 
the  flues  to  the  front,  it  receives  very  little  heat  from  the  furnaces 
and  main  flues.  From  the  figures  it  will  be  seen  that  it  can  receive 
practically  no  heat  from  the  furnaces,  because  the  ash-pit,  which 
forms  about  half  of  the  area  of  the  furnace,  and  which  is  occupied 
practically  by  hot  air  only,  is  interposed  between  the  fire-bars  on 
which  the  burning  fuel  rests,  and  the  bottom  of  the  furnace.  In 
addition  to  this,  the  natural  tendency  of  hot  fluids,  using  the  term 
in  its  scientific  sense  to  mean  liquids  and  gases,  to  rise  when  heated, 
keeps  the  hot  gases  in  the  flues  to  their  upper  portions,  and  therefore 
very  little  heat  passes  from  them  to  the  water  below.  As  will  be 
seen  later  on,  this  is  not  altogether  an  unmixed  evil.  As  explained 
in  the  first  chapter,  the  water  available  for  boilers  is  only  pure  when 
it  is  evaporated  specially  for  the  purpose,  or  when  the  condensed 
exhaust  steam  is  used  again,  and  only  then  after  it  has  been  subjected 
to  a  process  of  purification.  Hence  it  is  of  importance  that  there 
should  be  some  part  of  the  boiler  where  the  foreign  bodies  present 
in  the  water  can  deposit,  with  as  little  harm  as  possible,  and  in  the 
Lancashire  and  Cornish  boilers  the  bottom  of  the  boiler  is  the  place 
where  foreign  matter  -  falls.  A  mud  hole,  as  it  is  called,  as  shown 
in  Figs.  5  and  6,  and  Plates  IA,  2A,  2B,  and  2c,  and  sometimes  a  mud 
drum,  is  fixed  at  a  convenient  part  of  the  bottom  of  the  boiler, 
usually  at  the  back  end,  for  the  purpose  of  getting  rid  of  all  these 
foreign  substances,  the  deposit  being  periodically  blown  out  by  the 
scum  cock  provided  for  the  purpose. 

On  the  other  hand,  the  question  of  the  circulation  in  the  boiler 
is  a  very  important  one,  and  for  that  reason  a  number  of  adjuncts 
have  been  added  to  boiler  plant,  all  aiming  at  carrying  the  water 
from  the  lower  part  of  the  boiler  to  the  upper  part,  and  that  above 
to  the  lower  part,  the  object  of  this  being  the  more  efficient  working 
of  the  boiler,  and  the  more  even  distribution  of  temperatures. 

The  Galloway  Cone  Tubes 

One  of  the  earliest  methods  of  increasing  the  circulation  of  the 
water  in  the  boiler,  and  at  the  same  time  of  increasing  the  extent 
of  metal-heating  surface  in  the  boiler,  was  the  Galloway  tube. 

It  will  have  been  noticed,  in  the  description  given  above  of  the 


60      STEAM    BOILERS,   ENGINES,   AND   TURBINES 

path  of  the  gases  generated  in  the  boiler  furnace,  that  in  both  Lanca- 
shire and  Cornish  boilers  one  object  endeavoured  to  be  attained  was, 
the  exposure  of  the  largest  water  surface  to  metal  plates,  on  the  other 
side  of  which  the  hot  furnace  gases  were  passing,  every  part  of  the 
boiler  in  which  water  is  present,  it  will  be  remembered,  being 
traversed  by  the  hot  gases  before  finally  passing  to  the  chimney. 
One  advantage  possessed  by  the  Lancashire  boiler  over  the  Cornish 
boiler  is,  the  fact  that  practically  double  the  heating  surface,  as  it  is 
termed,  the  hot  metal  surface  against  which  water  presses,  is  present. 
The  Galloway  tube,  which  was  introduced  first  as  a  simple  cylindrical 
tube,  and  afterwards  as  one  having  the  shape  of  a  frustrum  of  a  cone, 
was  brought  out  as  far  back  as  1849.  It  was  made  in  conical  form 
in  1851,  and  after  passing  through  the  usual  developments,  has  finally 
settled  down  to  the  form  at  present  employed,  in  which  the  diameter 
of  the  upper  end  is  twice  that  of  the  smaller  end,  the  figures  being 
usually  10J  inches  diameter  at  the  top  and  5J-  inches  at  the  bottom, 
and  with  very  small  flues  9  inches  at  the  top  and  4^  inches  on  the 
bottom.  The  Galloway  cone  tubes  are  now  employed  in  large  numbers 
of  both  Cornish  and  Lancashire  boilers,  and  they  are  fixed  in  the 
flues  beyond  the  furnace  in  varying  numbers,  according  to  the  design 
of  the  different  makers.  Fig.  6,  and  Plates  IA,  2A,  2B  and  3A, 
show  the  arrangement  of  the  ordinary  Cornish  and  Lancashire  boilers, 
with  the  cone  tubes.  It  will  be  understood  from  what  has  been  said, 
that  the  cone  tubes  increase  the  space  occupied  by  the  water  with 
any  given  size  of  boiler,  and  they  also  increase  the  metal  surface 
exposed  to  the  hot  gases,  having  water  on  the  other  side.  The  presence 
of  the  cone  tubes  also  furnishes  paths  for  the  water  to  pass  from  the 
bottom  to  the  top,  and  vice  versa,  and  so  considerably  aids  the  circula- 
tion, thereby  increasing  the  efficiency  of  the  boiler  as  a  whole.  In 
addition  to  this,  the  presence  of  the  cone  tubes  materially  strengthens 
the  boiler  flues.  It  will  be  understood  from  the  sectional  drawings 
in  Figs.  5  and  6,  and  Plates  IA,  IB,  2A,  2B  and  2c,  that  in  both  the 
Cornish  and  Lancashire  boilers  the  outside  vessel  consists  of  a  cylinder 
of  a  certain  length,  usually  with  flat  ends,  and  carrying  the  one  or 
two  cylindrical  tubes  suspended  inside  the  outer  shell,  and  supported 
by  the  ends,  and  by  the  buoyancy  of  the  water.  Hence  anything 
which  tends  to  strengthen  the  flue  as  a  whole,  to  enable  it  to  resist  the 
forces  tending  to  its  deformation,  such  as  the  heat  from  the  hot  gases,  etc., 
tends  to  lengthen  the  life  of  the  boiler,  and  to  reduce  the  repairs  bill. 

The  Construction  of  Lancashire  and  Cornish 

Boilers 

The  construction  of  Lancashire  and  Cornish  boilers  is  carried  out 
on  almost  identical  lines,  the  differences  in  the  boilers  being  those 


BOILERS  6 1 

stated,  the  one  having  only  one  flue  against  the  other's  two.  For  the 
manufacture  of  all  classes  of  boilers,  it  should  be  mentioned,  elaborate 
and  very  powerful  machinery  has  been  worked  out,  to  enable  manu- 
facturers to  handle  the  large  steel  and  iron  plates  dealt  with,  and 
to  save  labour  in  the  manufacture.  All  classes  of  Lancashire  and 
Cornish  boilers  have  their  shells  made  of  Siemens  Martin  open- 
hearth  steel,  having  a  tensile  strength  of  from  26  to  30  tons  to  the 
square  inch,  and  one  of  the  first  things  the  boiler-maker  sees  to  is 
that  the  steel  plates  that  are  delivered  to  him  comply  with  this 
requirement,  and  also  have  a  certain  elasticity  and  ductility.  Samples 
of  the  plates  taken  at  random  are  tested  in  machines  specially  de- 
signed for  the  purpose,  for  their  breaking  strain  and  the  elongation. 
The  breaking  strain  must  be  from  26  to  30  tons  to  the  square  inch, 
and  the  elongation  must  be  20  per  cent,  in  a  length  of  10  inches, 
without  breaking. 

The  boiler  shells  are  built  up  of  a  succession  of  circular  rings,  as 
will  be  seen  from  an  inspection  of  a  complete  Lancashire  boiler,  as 
shown  in  Plate  IA,  the  size  of  each  ring  depending  upon  the  diameter 
of  the  finished  boiler,  and  the  number  of  rings  upon  the  length  of  the 
boiler.  Each  ring  is  made  from  a  flat  plate,  which  has  had  its  edges 
planed  to  a  bevel,  and  is  bent  round  to  a  circle,  usually  by  vertical 
plate-bending  rolls.  The  two  ends  of  the  plate  are  united  together 
to  form  the  ring,  either  by  lap  joints  or  by  butt  joints,  the  latter 
being  the  more  frequent  arrangement.  In  the  lap  joint  one  edge  of 
the  plate  is  lapped  over  the  other,  and  the  two  are  bolted  together 
by  rivets.  In  the  butt  joint  the  two  edges  are  butted  together;  the 
bevels,  which  are  fullered  by  a  special  tool  to  enable  them  to  bed 
well  against  each  other,  are  brought  together,  and  two  short  plates, 
one  inside  and  one  outside,  are  bolted  across  the  butt  by  rivets.  In 
days  gone  by  it  was  common  to  punch  holes  in  the  steel  and  iron 
plates  that  are  employed  in  boiler-making,  with  the  twofold  result 
chat  the  holes  were  often  not  exactly  in  the  position  they  should  be, 
and  special  tools  had  to  be  employed  to  work  the  holes  opposite  each 
other,  and  to  get  the  rivets  in  place,  and  a  process  of  caulking  the 
seam  had  to  be  resorted  to  after  the  boiler  was  complete.  Further,  it 
has  been  shown  that  the  process  of  punching  the  plate  deteriorates 
the  substance  of  which  it  is  composed,  and  hence  the  practice 
now  is,  that  all  holes  required  for  rivets  or  other  purposes  in  any 
part  of  the  boiler  shell,  are  either  drilled  or  turned  by  proper 
machinery,  that  does  not  injure  the  material,  and  that  will  work 
truly  in  the  modern  sense.  For  the  rings  of  boiler  shells,  it  is 
usual  to  have  a  number  of  drills  in  one  frame,  standing  vertically 
one  above  the  other,  and  drilling  several  holes  at  the  same  time,  this 
ensuring  that  the  holes  shall  be  truly  in  line,  and  enabling  the  work 
to  be  done  rapidly.  The  ring  to  be  drilled  is  mounted  in  a  vertical 


62       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

position,  in  a  frame  provided  for  it,  which  holds  it  rigidly,  the  drilling 
machines  then  being  brought  into  position,  and  drilling  the  holes  as 
described.  Care  is  taken  to  break  joint,  as  it  is  termed,  in  the  suc- 
cessive longitudinal  seams  of  the  different  rings.  The  seam  of  each 
ring  comes  opposite  a  space  in  the  ring  on  each  side  of  it,  where  there 
is  no  joint. 

The  ends  of  Lancashire  and  Cornish  boilers  are  made  of  masses  of 
sheet  steel,  of  the  same  tensile  strength  as  that  from  which  the  rings 
are  made.  They  are  turned  to  a  complete  circle,  and  at  the  same 
time  the  one  or  two  holes  required  for  the  one  or  two  flues  are  bored 
out  of  them,  in  the  proper  positions,  by  tools  arranged  for  the  purpose. 
The  end  plates  are  also  drilled  in  very  much  the  same  manner  as 
the  shells  of  which  the  ring  is  composed,  and  they  are  secured  to  the 
end  rings  of  the  shell,  either  by  flanges  formed  on  the  plate  them- 
selves, or  by  angle  rings,  and  in  other  ways.  The  end  plates  are 
further  held  to  the  end  rings  of  the  shells  by  what  are  known  as 
gusset  stays,  practically  angle  pieces  secured  to  the  end  plates,  and 
to  the  inside  of  the  boiler  shells. 

In  some  forms  of  Lancashire  and  Cornish  boilers  the  ends  are 
made  either  egg-shaped  or  dish-shape,  the  object  in  these  forms  being 
the  avoidance  of  the  necessity  of  the  gusset  stays.  With  these  forms 
the  ends  of  the  boilers  are  made  just  the  size  to  fit  inside  the  end 
ring  of  the  shell,  the  two  being  then  drilled  and  riveted  together. 

Eiveting  is  nearly  always  done  by  hydraulic  pressure.  The 
operation  requires  two  men,  one  standing  inside  the  boiler  to  be 
riveted,  and  manipulating  what  is  called  a  "  dolly,"  or  holder-up, 
which  is  practically  a  chock  to  take  the  thrust  of  the  rivet.  The 
rivet  is  placed  in  the  hole,  the  hydraulic  riveter  brought  against  it, 
and  its  end  expanded  over  the  hole,  in  the  same  manner  as  cleating, 
the  arrangement  making  a  very  sound  and  economical  joint. 

Cornish  boilers  are  made  usually  for  lower  powers  than  Lancashire 
boilers,  and  in  smaller  sizes.  The  Cornish  boiler  is  made  from  3  feet 
6  inches  in  diameter  up  to  7  feet  in  diameter,  and  from  9  feet  in  length 
up  to  30  feet,  the  evaporative  power  ranging  from  700  Ibs.  of  water 
per  hour  up  to  3500.  The  Lancashire  boiler  is  made  from  5  feet 
6  inches  in  diameter  up  to  9  feet,  and  from  14  feet  in  length  up  to 
32  feet. 

The  single  flue  of  the  Cornish  boiler  was  originally  larger  than 
either  of  the  two  flues  of  the  Lancashire  boiler,  but  modern  practice 
has  settled  down  to  flues  of  about  the  same  size,  and  though  they 
vary  with  different  makers,  they  are  approximately  half  the  diameter 
of  the  boiler,  the  flues  of  the  larger  sizes  of  Lancashire  boilers  being 
rather  less  than  this. 

The  Lancashire  boilers  evaporate  from  1600  Ibs.  to  9000  Ibs.  of 
water  per  hour. 


BOILERS  63 

Cornish  boilers  are  occasionally  made  with  their  flues  eccentric 
to  the  outer  shell. 


Lancashire  and  Cornish  Boiler  Flues 

The  Lancashire  and  Cornish  boiler  flues  are  constructed  in  several 
different  ways.  The  simplest  arrangement  is,  the  flue  is  formed  of 
successive  lengths  of  rings,  of  the  diameter  the  flue  is  to  take.  The 
rings  are  formed  of  mild  steel  plates,  bent  to  the  form  of  a  cylinder, 
by  bending  rolls,  in  the  same  manner  as  described  for  the  boiler 
shell,  the  ends  of  the  plate  being  usually  welded  together.  In  some 
forms  of  boiler,  and  by  some  makers,  the  ends  of  the  plates  forming 
the  rings,  are  drilled  and  riveted  together,  in  the  same  manner  as 
described  for  the  boiler  shell,  but  welding  is  far  more  common.  The 
successive  lengths  are  connected  together  in  the  simple  form  of  flue, 
by  flanged  joints.  A  flange  is  formed  in  the  end  of  each  ring  of  the 
flue,  and  out  of  the  ring  itself,  by  a  special  flanging  machine,  the  two 
flanges  of  successive  rings  being  drilled  and  riveted  together.  The 


FIG.  7. — Section  of  the  Adamson 
original  Flange  Seam  for  Lan- 
cashire Boiler  Flues. 


FIG.  8. — Section  of  the  Adamson 
absorber  Flange  Seam  for  Lanca- 
shire Boiler  Flues. 


simple  form  of  flue  has,  however,  been  departed  from  by  many 
manufacturers,  for  the  reason  that  the  simple  riveted  flanged  joint 
frequently  gave  way.  One  method  that  has  been  adopted  is  what  is 
known  as  the  Adamson  joint,  in  which  an  additional  ring  is  placed 
between  the  two  flanges,  as  shown  in  Fig.  7,  the  whole  being  riveted 
together.  Messrs.  Daniel  Adamson  &  Son  have  also  since  intro- 
duced another  form  of  joint  for  the  sections  of  boiler  furnaces  and 
flues.  It  is  shown  in  Figs.  8  and  9,  and  is  claimed  to  give  increased 
strength  and  increased  heating  surface,  and  to  automatically  take  up 
its  own  expansion  and  contraction  with  heating  and  cooling.  As  will 
be  seen  from  Figs.  8  and  9,  the  difference  between  the  new  form  of 
joint,  named  by  the  firm  the  "Adamson  absorber  flange  seam"  is, 
the  successive  rings  of  which  the  flue  is  built  up  are  of  different 


64      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

diameters,  this  it  is  claimed  giving  the  expansibility  required. 
Another  method  of  jointing  the  successive  rings  of  the  flues  has 
been  introduced  by  Messrs.  Davey,  f  axman  &  Co.  One  end  of  each 
of  the  sections  is  expanded  by  special  tools,  to  a  certain  diameter, 


i 
i 
i 

i   J 


FIG.  9. — Sectional  Elevation  and  Plan  of  a  Lancashire  Boiler,  having  its  Flues  fitted  with 

Adamson's  Absorber  Flange. 

and  the  end  which  is  to  unite  with  it  of  the  next  flue,  is  also 
expanded  to  a  certain  extent,  but  to  a  diameter  that  will  enable  it 
to  just  fit  inside  the  end  of  the  next  section  it  is  to  engage  with. 
The  two  flanges,  when  fitted  together,  are  drilled  by  special  drilling 
machines,  and  are  then  riveted  by  hydraulic  rivets.  It  is  claimed 
by  Messrs.  Davey,  Paxman,  that  this  arrangement  provides  for  the 
expansion  and  contraction  in  the  same  manner  as  the  Adamson  joint. 


Corrugated  Flues  and  Furnaces 

Another  form  of  furnace  and  flue  that  is  made  by  several  firms, 
is  that  known  as  the  corrugated  flue.  As  its  name  implies,  the  flue 
is  built  up  of  a  succession  of  rings,  as  in  the  ordinary  flue,  but  the 
rings  are  of  the  corrugated  form.  There  are  two  forms  of  the 


PLATE  2A. — Galloway  Lancashire  boiler,  showing  the  cone  tubes,  and  the  special 
arrangement  of  the  two  flues  behind  adopted  by  Messrs.  Galloway,  also  the 
pockets  in  the  sides  of  the  flues. 


PLATE  2B. — Battery  of  Galloway  Lancashire  boilers,  adopted  for  burning  low  grade 
fuels.  The  furnace  is  shown  in  front,  with  a  connection  to  the  boiler  flues.  The 
side  flues  and  bottom  flues  are  also  shown. 


PLATE  2c.— Galloway  multitubular  boiler,  with  external  firing,  showing  the  furnace 

and  the  side  flues.  [To  face  p.  64. 


BOILERS  65 

corrugated  flue  on  the  market.  In  the  earlier  form  each  successive 
ring  is  merely  corrugated,  very  much  on  the  lines  of  the  well-known 
corrugated  iron  plates  that  are  employed  for  building,  etc.  In  later 
patterns  the  corrugation  has  taken  a  special  form,  in  which  there  are 
ridges  at  definite  distances  along  the  length  of  the  furnace,  separated 
by  valleys  that  are  almost  level,  or  only  slightly  raised  in  the  centre. 
The  object  of  the  corrugated  flue  is  to  give  greater  strength  to  resist 
the  pressures  to  which  the  flues  and  furnaces  are  subject.  In  some 
of  the  early  furnaces  that  were  made  without  any  protection  whatever, 
the  furnace  collapsed  in  places,  owing  to  the  extreme  pressure  brought 
to  bear  on  it  by  the  water  and  the  steam  above  it.  In  addition  to  this, 
it  often  happens  that  there  is  a  deposit  from  the  water  employed  in 
the  boiler  on  the  top  of  the  furnace  crown,  and  this,  .especially  when 
the  deposit  is  of  oil,  such  as  is  frequently  brought  over  from  the 
engine  through  the  condenser,  is  such  that  a  resistance  is  set  up  to 
the  passage  of  heat  from  the  burning  fuel  to  the  water  lying  on  the 
top  of  the  furnace,  the  result  being  that  the  crown  of  the  furnace 
itself  is  raised  to  a  high  temperature,  its  tensile  strength  being  then 
considerably  reduced,  and  collapse  resulting.  The  forms  described 
give  very  much  greater  strength,  it  is  claimed,  to  resist  the  pressure 
mentioned,  and  in  addition  they  tend  to  reduce  the  tendency  of  the 
oil  and  other  matters  to  deposit. 

These  forms  of  furnaces  are  made  by  the  Leeds  Forge  Company, 
under  the  name  of  the  Morrison  Suspension  Furnace,  and  one  form 
of  their  furnace  is  arranged  to  be  withdrawn  from  a  marine  boiler 
without  dismantling  the  boiler  itself.  Messrs.  John  Brown  &  Co. 
also  make  two  forms  of  the  furnace,  one  of  which  they  have  named 
their  Improved  Furnace,  and  the  other  the  Cambered  Furnace,  the 
difference  between  the  two  being  the  arrangement  of  the  corrugations. 
Messrs.  Deighton  &  Co.  also  make  two  forms,  one  in  which  the 
corrugations  are  simply  hills  and  valleys,  and  the  other  in  which 
the  space  between  the  hills  is  also  slightly  corrugated. 

All  of  these  firms  have  had  tests  carried  out  to  meet  the  Board 
of  Trade,  Lloyds,  and  the  Bureau  Veritas  requirements  for  furnaces 
that  are  employed  on  board  ship,  and  the  following  formulae  are 
given  for  the  working  pressures  for  the  different  forms  of  corrugated 
furnaces,  that  is  to  say,  the  working  pressure  of  the  boiler  to  which 
the  furnaces  are  applied. 

The  formulae  are  as  follows : — 

14000 
For  the  Board  of  Trade,  W.P.  =  - 

For  Lloyds  and  the  Bureau  Veritas,  W.P.  = 

The  British  Corporation,  W.P.  =  I160  XT  " 


66      STEAM   BOILERS,   ENGINES,   AND   TURBINES 


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68       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

In  the  above  formulae  W.P.  is  the  working  pressure,  T  is  the 
thickness  of  the  plate  from  which  the  furnace  is  made  in  sixteenths 
of  an  inch  for  the  Board  of  Trade,  D  is  the  greatest  diameter  of  the 
flue  in  inches. 

The  Board  of  Trade,  in  the  United  Kingdom,  has  complete 
command  over  all  that  shall  be  done  in  the  matter  of  steam 
appliances  on  British-owned  ships,  and  their  surveyors  are  constantly 
in  evidence  at  seaports,  to  see  that  their  rules  are  carried  out. 
Lloyds  and  the  British  Corporation  are  insurance  companies,  who 
insure  ships,  and  also  keep  their  surveyors  at  every  port  to  see  that 
their  requirements  are  carried  out.  The  Bureau  Veritas  is  a  French 
company,  similar  to  Lloyds  in  this  country,  and  it  keeps  its  surveyors 
in  all  ports.  The  table  on  pages  66  and  67  gives  the  working  pres- 
sures of  boilers  to  which  the  corrugated  flues  are  fixed,  according  to  the 
above  formulae,  as  allowed  by  the  Board  of  Trade,  and  by  Lloyds  and 
the  Bureau  Veritas.  The  figures  on  the  extreme  left  and  the  extreme 
right  of  the  table,  are  the  smallest  internal  diameters  of  the  furnaces 
inside  of  the  corrugations.  The  figures  at  the  top  of  the  tables, 
-j7^  inch,  J|  inch,  and  so  on,  are  the  thickness  of  the  plates  from 
which  the  furnaces  are  made,  and  the  figures  below  each  plate 
thickness  are  the  pressures  allowed  respectively  by  the  Board  of 
Trade  and  Lloyds  and  Bureau  Veritas,  with  the  given  thickness  of 
plate,  and  the  given  size  of  furnace.  It  will  be  noticed,  in  glancing 
down  the  table,  that  the  pressure  allowed,  though  it  varies  between 
the  Board  of  Trade  and  the  insurance  companies,  follows  in  both 
cases  two  simple  laws.  The  pressure  that  may  be  allowed  increases 
with  the  thickness  of  the  plate  of  which  the  furnace  is  composed,  and 
nearly  in  proportion  to  that  thickness,  as  expressed  by  the  formulae, 
where  T  —  2  is  one  of  the  factors.  The  pressure  that  is  allowed  also 
deceases  with  all  thicknesses  of  plate,  as  the  diameters  of  the  furnaces 
increase. 


Setting  Cornish  and  Lancashire  Boilers 

It  has  been  mentioned  above  that  Cornish  and  Lancashire  boilers 
have  brickwork  flues  provided  for  the  hot  gases,  underneath  the 
boiler,  and  at  its  side.  This  entails,  as  will  easily  be  understood,  the 
formation  of  the  brickwork  setting,  with  which  every  one  who  has 
visited  a  boiler-house,  is  familiar.  Two  points  should  be  noted  in 
connection  with  the  boiler  brickwork.  The  brickwork  should  be 
so  arranged  as  to  efficiently  support  the  boiler,  and  to  provide  flues 
that  can  easily  be  cleaned;  but  the  support  of  the  boiler,  and  the 
arrangement  of  the  flues  must  be  such  that  the  brickwork  does  not 
carry  off  heat.  To  meet  this  requirement  the  support  of  the  boiler 


BOILERS  69 

underneath  should  be  by  blocks  of  sections  designed  to  offer  a  good 
support  to  the  boiler,  while  at  the  same  time  offering  a  high  thermal 
resistance,  by  small  contact  with  the  mass  of  the  boiler.  Further, 
the  brickwork  should  be  so  arranged  as  to  offer  the  highest  possible 
resistance  to  the  passage  of  heat  through  it.  In  America  a  firm 
known  as  the  McLeod.  and  Henry  Company  make  what  they  call 
a  steel  mixture,  which  is  employed  for  the  purpose,  and  which  is 
stated  to  be  stronger  and  more  durable,  and  to  be  more  refractory 
than  ordinary  firebrick,  the  fusing-point  of  the  mixture  being  given 
as  4000°  F. 

Messrs.  McLeod  and  Henry  advise  the  formation  of  a  back  arch 
for  the  connection  between  the  boiler  flues  and  the  side  flues,  etc. 

Another  important  point  is,  the  brickwork  should  be  quite  air- 
tight. One  of  the  causes  of  loss  of  heat  in  boiler  services  where 
brick  flues  are  employed  is,  air  filters  through  the  joints  of  the 
brickwork,  and  mingles  with  the  hot  gases  passing  through  them, 
lowering  their  temperature  by  the  absorption  of  heat  from  the  hot 
gases  to  raise  the  temperature  of  the  incoming  air  to  that  of  the  gases 
themselves.  Every  cubic  foot  of  air  passing  in  absorbs  about  20 
B.  Th.  units. 


Firing  Lancashire  and  Cornish  Boilers  from 

Outside 

It  will  be  understood  that  one  of  the  important  features  of  both 
the  Cornish  and  Lancashire  boilers  is  the  internal  firing,  the  furnace 
being  completely  surrounded  by  the  water  of  the  boiler,  the  whole 
of  the  heat  liberated  by  the  combustion  of  the  fuel  being  delivered 
within  the  boiler,  and  therefore  being  in  the  best  position  for 
efficiency.  With  some  forms  of  fuel,  however,  it  is  not  possible  to 
arrange  this.  As  explained  in  the  first  chapter,  with  low  grade  fuels, 
such  as  the  refuse  from  sugar-canes,  cotton,  saw  mills,  etc.,  which 
are  very  valuable  as  fuels  in  certain  parts  of  the  world,  much  larger 
quantities  have  to  be  consumed  than  is  necessary  with  good  coals, 
and  hence  a  larger  grate  area,  and  a  larger  furnace  generally  must  be 
provided,  and  this  necessitates  a  furnace  being  placed  outside  of  the 
boiler.  This  is  the  position  the  furnace  occupied  in  the  early  days 
of  boiler  work,  and  it  also  occupies  that  position  with  several  other 
forms  of  boiler.  There  are  two  methods  that  may  be  employed  witli 
external  firing.  The  furnace  may  be  carried  underneath  the  bottom 
of  the  boiler,  as  shown  in  Plate  2c,  the  hot  gases  passing  through 
a  flue  built  for  it  under  the  boiler,  returning  through  the  flues  on 
the  inside  of  the  boiler  to  the  front,  and  thence  by  the  side  flues 
to  the  back  and  to  the  chimney.  Or  the  furnace  may  be  fixed 


yo       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

in  front  of  the  boiler,  the  boiler  flues  extending  the  whole  length 
of  the  boiler  shell,  and  the  furnace  gases  passing  straight  into  the 
flues  from  the  furnace,  and  afterwards  taking  their  usual  course.  A 
boiler  furnace  constructed  on  these  lines,  by  Messrs.  Galloway,  is 
shown  in  Plate  2B,  and  a  special  form  for  cane  refuse,  etc.,  in  Plate 
SA.  Messrs.  Meldrum  have  also  adopted  this  plan  in  the  furnace 
they  have  arranged  for  burning  colliery  and  other  refuse. 

The  Galloway  Boiler 

As  already  mentioned,  the  Galloway  cone  tube  has  been  very 
largely  adopted,  and  is  fitted  to  the  flues  of  Lancashire  and  Cornish 
boilers  by  all  makers.  Messrs.  Galloway  themselves  have  evolved 
a  boiler  of  their  own,  of  the  Lancashire  type,  which  has  been 
developed  around  the  experiments  that  have  been  made  with  their 
cone  tube,  and  which  differs  in  several  respects  from  the  ordinary 
Lancashire  boiler.  The  first  difference  is,  while  the  two  furnaces  are 
kept  separate,  the  two  flues  into  which  the  furnaces  open  are  made 
into  one. 

The  joint  flue  was  first  developed  of  an  elliptical  section,  but  has 
since  been  altered  to  one  in  which  the  upper  and  lower  walls  of  the 
flue  are  parts  of  concentric  circles,  the  two  arcs  being  set  up  with 
different  radii  from  one  centre,  and  the  cone  tubes  are  inclined 
radially  towards  each  other.  The  result  of  this  is  stated  to  be  the 
production  of  a  very  successful  boiler,  and  a  good  circulation  through 
the  cone  tubes. 

In  addition  to  the  above,  Messrs.  Galloway  form  pockets  in  the 
sides  of  the  flues,  the  object  of  this  being  to  increase  the  heating 
surface,  and  to  aid  in  strengthening  the  flue.  These  points  are  shown 
in  Plates  2A  and  2B. 


Multitubular  Boilers 

In  describing  the  Lancashire  and  Cornish  boilers,  it  was  mentioned 
that  the  arrangement  of  the  flues  was  designed  to  provide  as  large  a 
heating  surface  as  possible,  that  is  to  say,  to  divide  up  the  water  in 
the  boiler  as  much  as  possible,  and  to  bring  as  many  parts  of  it  as 
possible  in  contact  with  some  hot  plate  having  hot  gases  on  its  other 
side.  The  multitubular  boiler,  in  its  somewhat  various  forms,  is 
designed  to  still  further  accomplish  this,  and  any  one  of  the  boilers 
made  on  this  pattern  will  furnish  a  given  quantity  of  steam  from  a 
boiler  of  very  much  smaller  size  than  either  the  Lancashire  or 
Cornish,  designed  for  the  same  work. 


BOILERS  71 

In  the  multitubular  boiler,  as  its  name  shows,  the  single  flue  of 
the  Cornish  boiler  and  the  two  flues  of  the  Lancashire  boiler  are 
displaced  by  a  large  number  of  very  much  smaller  tubes,  generally 
ranging  from  3  to  4  inches  in  diameter,  running  usually  from  end  to 
end  of  the  boiler.  The  hot  gases  pass  through  these  tubes,  the 
water  lying  all  around  the  tubes  in  the  space  not  occupied  by  them. 

The  principal  reason  why  multitubular  boilers  are  not  more 
employed  than  they  are,  seeing  the  greater  steaming  capacity  for  a 
given  weight  and  size,  is  the  difficulty  of  cleaning  them.  In  every 
boiler  there  are  two  surfaces  upon  which  deposit  takes  place,  both  of 
which  tend  to  offer  resistance  to  the  passage  of  heat  from  the  hot 
gases  to  the  water — viz.  the  surface  in  contact  with  the  gases,  on 
which  finely  divided  carbon,  or  soot,  is  apt  to  collect,  and  the  surface 
in  contact  with  the  water,  upon  which  the  salts  carried  by  the  water 
are  also  apt  to  deposit.  In  the  case  of  tubular  boilers,  it  is  not  very 
difficult  usually  to  clean  the  tubes,  but  it  is  exceedingly  difficult  to 
clean  the  water  space  between  them,  more  particularly  as  the  sub- 
stances which  are  deposited  upon  the  metal  there  are  very  clinging. 
The  salts  that  are  carried  by  the  water  are  often  combined  with  some 
of  the  oil  that  has  been  employed  for  lubricating  the  engine,  and 
that  has  been  carried  as  vapour,  or  in  a  finely  divided  state,  into  the 
condenser,  and  has  found  its  way  back  from  the  condenser  into  the 
boiler.  The  substance  formed  by  the  oil  and  the  salts  is  particularly 
tenacious,  and  offers  a  very  high  resistance  to  the  passage  of  heat 
through  it. 

In  the  multitubular  boiler,  which  is  usually  fired  from  a  furnace 
below  the  bottom  of  the  boiler,  the  hot  gases  pass  from  the  back  of 
the  boiler  through  the  tubes  to  the  front,  and  thence  by  the  side  flues 
to  the  chimney.  The  gases,  it  will  be  seen,  split  up  at  the  back  of 
the  boiler  into  small  sections,  each  section  passing  through  its  own 
tube,  the  whole  reuniting  at  the  front  and  passing  to  the  sides,  as 
explained.  The  heating  surface,  the  quantity  of  metal  plate  in  the 
multitubular  boiler,  acting  as  a  separator  between  the  hot  gases  and 
the  water,  is  enormously  increased,  and  in  addition,  the  mass  of  the 
hot  gases  being  so  divided,  the  gases  themselves  very  much  more 
readily  part  with  their  heat  to  the  metal  tubes  surrounding  them, 
because  there  is  a  smaller  core  of  gas  in  each  of  the  tubes.  It  will 
be  understood  that  when  hot  gases  are  passing  through  the  flues  of 
Lancashire  or  Cornish  boilers,  the  gases  that  are  in  contact  with  the 
shells  of  the  flues  are  doing  the  most  work,  because  the  gases  them- 
selves do  not  conduct  heat  very  readily,  and  therefore  the  heat  from 
the  inside  mass  cannot  easily  reach  the  metal  plates  of  which  the 
flues  are  composed.  This  is  one  of  the  reasons  why  the  Galloway 
cone  tube  so  increases  the  efficiency  of  the  Lancashire  and  Cornish 
boilers,  because  it  breaks  up  the  hot  gases,  as  well  as  providing 


72      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

heating  surface,  and  in  the  multitubular  boiler,  it  will  be  seen,  the 
process  is  carried  very  much  further. 


Forms  of  Multitubular  Boiler 

There  are  several  forms  of  multitubular  boilers,  known  by  various 
names,  and  having  slightly  different  construction,  according  to  the 
purpose  for  which  they  are  employed.  They  are  known  as  the  Marine 
boiler,  the  Locomotive  boiler,  the  Dry-Back  boiler,  and  simply  the  Mul- 
titubular boiler.  In  all  of  them  there  is  the  nest  of  tubes  through 
which  the  hot  gases  pass.  In  the  marine  boiler,  the  dry-back  boiler, 
and  the  ordinary  multitubular  boiler,  the  hot  gases  pass  from  the 
back  of  the  boiler  through  the  tubes  to  the  front.  In  the  locomotive 
boiler  they  may  pass  from  the  front — that  is,  directly  from  the  fire- 
box to  the  back  of  the  boiler.  In  the  case  of  the  locomotive  employed 
on  railways,  the  fire-box  is  at  the  rear  of  the  boiler,  in  the  direction 
the  train  is  running,  and  in  that  case  it  would  be  proper  to  say  that 
the  hot  gases  pass  from  the  rear  to  the  front ;  but  they  pass  directly 
from  the  fire-box  into  the  fire-tubes,  without  changing  their  direc- 
tion, and  thence  to  the  smoke-box  and  up  the  chimney,  while  in  the 
remaining  forms  of  multitubular  boiler,  the  direction  of  flow  of  the 
gases  is  reversed  after  leaving  the  fire-box  or  the  combustion  chamber 
beyond.  Plate  SB  shows  a  multitubular  boiler  made  by  the  Atlas 
Co.  of  America. 


The  Ordinary  Multitubular  Boiler 

The  ordinary  multitubular  boiler  has  been  partially  described 
above.  As  made  by  Messrs.  Davey,  Paxrnan  &  Co.,  it  takes  two 
principal  forms,  known  as  the  English  and  American  pattern.  The 
English  pattern  consists  of  a  short  cylinder,  with  tubes  occupying 
the  lower  portion,  the  furnace  being  fixed  below  the  boiler,  which  is 
set  in  brickwork  in  the  usual  way,  and  a  mud  drum  is  fixed  below 
the  boiler,  and  at  right  angles  to  it,  with  an  entrance  into  the  back 
of  the  boiler,  to  receive  the  deposit  from  the  water,  as  explained  in 
previous  sections,  the  boiler  being  set  in  brickwork.  The  course  of 
the  gases  in  this  form  is  from  the  furnace,  past  the  fire-brick  bridge 
at  the  end  of  the  furnace,  to  the  combustion  chamber  at  the  back, 
thence  through  the  tubes  to  a  brick  smoke-box  in  the  front,  thence 
through  the  side  flues  to  the  chimney.  In  the  American  pattern 
made  by  this  firm,  the  chimney  is  at  the  front,  where  it  opens  from  a 
cylindrical  smoke-box,  and  the  boiler  is  supported  from  iron  girders 
standing  upon  iron  columns,  instead  of  by  the  brickwork,  the  boiler 


PLATE  3 A. — Furnace  and  part  of  flues  of  Galloway  boiler  arranged  for  burning  wood, 
gas  coal,  etc.  The  fuel  falls  down  the  steps  shown,  as  it  consumes,  and  the  hot 
gases  pass  up  into  the  boiler  flues. 


PLATE  SB. — Externally  fired  multitubular  boiler,  as  made  by  the  Atlas  Co. 


PLATE  3c. — Locomotive  type  of  .boiler,  as  adopted  for  portable  engines  by  Messrs. 

Marshall.  [  To  face  p.  72. 


j  i  V  r  q 


BOILERS 


73 


itself  being  built  in  by  brickwork,  something  on  the  lines  of  the 
water-tube  boiler,  explained  later,  and  the  gases  pass  over  the  whole 
of  the  outside  shell  of  the  boiler,  and  through  the  tubes  to  the  front. 
There  is  also  a  cylindrical  drum  fixed  above  the  iron  girders,  for  the 
reception  of  the  steam. 


The  Locomotive  Type  of  Boiler 

The  locomotive  type  of  boiler  is  very  much  employed  for  portable 
boilers,  carrying  engines  above  or  below  them,  such  as  those  used  for 
traction  purposes,  and  for  agricultural  purposes,  driving  thrashing 
machines,  etc.     It   is   also   used   largely  for   semi-portable  boilers, 
for  temporary  work,  such  as  contractor's  work  on  docks,  waterworks, 
railways,  etc.,  the   reason  being  that  it   is  easily  and  quickly  set 
up,  and  easily  and  quickly  removed  when  required.     In  the  locomo- 
tive type  of  boiler,  only  as  much  of  the  heat  of  the  flue  gases  can  be 
transmitted  to  the  water,  as  will  pass  across  from  the  tubes  to  the 
water  surrounding  them.     Use  cannot  be  made  of  the  outer  shell  of 
the  boiler,  in  the  manner  in  which  it  is  made  use  of  in  the  Lancashire 
and  Cornish  boilers ;  and  it  is  necessary  that  water  shall  be  present 
on  the  inside  of  the  boiler  shell  everywhere,  except,  of  course,  in  the 
fire-box,  and  as  far  as  possible  round  that  also.     With  the  multi- 
tubular  boiler,  as  will  be  understood  from  what  has  been  said  before, 
the  absence  of  the  side  and  bottom  flues  does  not  make  anything  like 
as  much  difference  to  the  economy  of  the  boiler  as  it  would  in  the 
case  of  the  Lancashire  and  Cornish  boilers,  because  the  flue  gases 
being  so  thoroughly  divided  up  by  the  fire-tubes,  the  heat  is  very 
much   more  taken  from  them   in  passing  through  the   tube,  than 
through  the  Lancashire  or  Cornish  flues.     In  the  portable  engines 
that  are  used  for  agricultural  and  traction  work,  the  tubes  are  made 
very  small,  but  they  are  easily  cleaned,  as  the  smoke-box  into  which 
the  tubes  open  at  the  funnel  end  is  closed  by  a  large  iron  door,  and 
when  this  door  is  open,  the  ends  of  the  fire  tubes  are  exposed  and 
are  easily  reached.     It  is  not  so  easy,  however,  to  clean  the  spaces 
between  the  tubes  in  which   the  water  lies,  and  in  which  deposit 
occurs,  and  therefore  in  all  boilers  of  this  kind  the  water   should 
be  as  soft  as  possible.     Plate  3c  shows  a  portable  boiler  of  this  type 
made  by  Messrs.  Marshall. 


The  Marine  Boiler 

In  the  marine  boiler  quite  another  set  of  conditions  has  to  be 
fulfilled.     The  boiler,  it  will  be  remembered,  is  fixed  on  board  ship, 


74       STEAM   BOILERS,   ENGINES,   AND    TURBINES 

as  near  the  middle  of  the  ship  as  possible.  It  has  to  be  practi- 
cally self-contained,  and  all  the  heat  that  is  extracted  from  the 
gases  must  be  obtained  without  the  aid  of  brick  or  similar  flues. 
Further,  conditions  of  safety  for  the  remainder  of  the  ship  demand 
that  there  shall  be  a  mass  of  water  for  the  hot  gases  to  impinge 
against  as  they  issue  from  the  furnace,  and  for  that  reason  the  marine 
boiler  is  known  as  the  "  Wet-Back "  boiler.  Its  construction  is  as 
follows :  It  may  be  circular  or  rectangular  in  section.  It  carries 
one,  two,  and  sometimes  three  furnaces  at  its  lower  part,  the  furnaces 
being  fixed  internally,  in  a  similar  manner  to  those  of  the  Lancashire 
and  Cornish  boilers,  and  the  space  above  the  furnace  is  filled  with  a 
nest  of  tubes,  as  shown  in  Plate  4A.  The  hot  gases  pass  from  the 
furnace  into  a  vertical  space  provided  for  them  at  the  back  of  the 
boiler,  thence  through  the  fire-tubes,  which  are  fixed  horizontally,  to 
a  smoke-box  in  front,  and  thence  to  the  funnel,  this  occupying,  as 
usual,  a  position  in  the  centre  of  the  ship.  At  the  back  of  the  com- 
bustion chamber,  into  which  the  furnace  gases  pass,  is  the  chamber 
containing  water,  which  communicates  with  the  space  surrounding 
the  fire-tubes,  and  also  extends  to  the  space  surrounding  the  furnaces. 
Where  the  boiler  is  of  the  cylindrical  form,  it  resembles  a  Lancashire 
or  Cornish  boiler  to  a  certain  extent,  as  will  be  seen  from  Plate  4A, 
but  it  is  very  much  shorter,  and  the  space  usually  occupied  by  the 
free  body  of  water  and  steam  is  occupied  by  the  tubes  with  the  steam 
space  above  them.  The  arrangement  of  the  furnaces  of  marine 
boilers  varies  somewhat,  some  of  them  being  known  as  "  dry  bottom," 
and  others  "  wet  bottom,"  the  difference  being,  with  the  dry  bottom 
there  is  very  little  water  below  the  furnaces,  and  in  the  wet  bottom 
there  is  a  fairly  considerable  quantity. 


The  Dry = Back  Boiler 

The  dry-back  boiler  is  really  a  form  of  the  ordinary  multitubular 
boiler,  or  it  may  be  considered  a  form  of  the  marine  boiler,  from  which 
it  is  distinguished  by  having  no  water  space  at  the  back  of  the  boiler, 
beyond  the  combustion  chamber  into  which  the  flue  gases  empty. 
The  dry-back  boiler  is  made  by  nearly  all  the  large  firms  ;  in  par- 
ticular, Messrs.  Davey,  Paxman  &  Co.  have  made  a  speciality  of  one 
which  they  call  their  "  Economic "  boiler.  In  this  form  of  boiler 
the  furnaces  are  carried  in  the  boiler,  or,  as  it  is  expressed,  the  boiler 
is  internally  fired,  just  as  the  Lancashire  and  Cornish  boilers  are,  and 
the  hot  gases  pass  into  a  combustion  chamber  at  the  back  of  the 
boiler,  thence  through  the  nest  of  tubes  mentioned,  to  a  smoke-box 
on  the  front,  thence  to  side  flues  formed  from  brickwork,  in  a  similar 
manner  to  the  Lancashire  and  Cornish  boiler,  and  thence  to  the 


BOILERS 


75 


76       STEAM   BOILERS,   ENGINES,   AND    TURBINES 

chimney.  The  boiler,  like  all  multitubular  boilers,  is  much  shorter 
than  the  Lancashire  and  Cornish  boiler,  and  is  of  about  the  same 
diameter,  for  the  same  evaporative  power,  and  is  set  in  brickwork  in 
a  similar  manner  to  the  Lancashire  and  Cornish  boilers.  It  is  shown 
in  Fior  10. 


Combined   Cornish  and   Multitubular  Boilers 

Another  form  of  boiler,  that  is  made  by  several  firms  in  this 
country,  and  in  America,  is  the  Combined  Cornish  and  Multitubular 
boiler.  It  is  made  in  several  forms  according  to  the  fancy  of  the 
makers.  In  one  form  made  by  Messrs.  Galloway,  there  are  two 
distinct  boilers,  or  rather  two  distinct  cylinders,  standing  one  above 
the  other,  connected  by  steam  pipes,  both  built  in  by  brickwork. 
The  lower  cylinder  is  the  Cornish  boiler  with  its  single  flue  and 
furnace,  inside  the  boiler  shell  as  before;  and  the  upper  cylinder 
is  shorter,  and  forms  the  multitubular  boiler.  Above  the  latter 
again  stands  a  smaller  cylinder  forming  the  steam  drum.  The  hot 
gases  pass  through  the  internal  flue  of  the  Cornish  boiler,  up  at  the 
back  of  the  boiler  to  the  multitubular  portion,  through  the  tubes 
to  the  front,  back  by  the  side  flues  of  the  multitubular  portion  to 
the  back  of  the  boiler,  then  from  the  side  flues  of  the  multitubular 
to  the  side  flues  of  the  Cornish  portion,  from  the  back  to  the  front 
end,  thence  into  the  bottom  flue  of  the  Cornish  portion  to  the  back 
end  and  to  the  chimney. 

Messrs.  Fraser  &  Chalmers  also  make  what  they  call  Compound 
Cornish  Multitubular  boilers,  the  ordinary  Cornish  single  flue 
occupying  the  front  portion  of  the  fire  space,  the  rear  portion  of  the 
space  usually  occupied  by  the  flue  being  filled  with  tubes.  The  hot 
gases  pass  from  the  furnace  over  the  fire-brick  bridge,  to  the  com- 
bustion chamber  at  the  back,  thence  through  the  tubes  to  the  back 
of  the  boiler,  and  thence  by  the  usual  paths  under  the  boiler,  and 
by  the  side  flues  to  the  chimney.  Messrs.  Marshall  make  a  boiler 
of  this  kind,  as  shown  in  Fig.  5. 

In  the  American  form,  known  as  the  Eobb-Mumford  boiler,  a 
section  of  which  is  shown  in  Fig.  11,  there  are  two  cylinders,  as  in 
the  Galloway  pattern,  connected  together  by  steam  and  water  pipes, 
but  the  office  of  the  upper  cylinder  is  merely  to  hold  the  water  and 
for  circulation.  The  lower  cylinder  is  slightly  inclined  to  the 
horizontal,  the  back  end  being  above  the  furnace  end.  The  furnace 
occupies  a  large  portion  of  the  lower  cylinder,  and  the  tubes  open 
directly  from  the  furnace,  very  much  as  in  the  case  of  the  locomotive 
boiler.  Both  cylinders  are  enclosed,  sometimes  in  brickwork,  and 
sometimes  by  steel  plates.  The  hot  gases  after  passing  through  the 


BOILERS 


77 


tubes,  return  to  the  chimney,  which  opens  from  a  smoke-box  in  front, 
passing  over  the  surfaces  of  both  the  lower  and  upper  cylinders. 


FIG.  11. — Sectional  View  of  Robb-Mumford  Standard  Boiler. 


Water-tube  Boilers 

In  water-tube  boilers,  as  their  name  implies,  the  conditions  ruling 
with  the  fire-tube  boilers  are  reversed — the  water  is  held  in  tubes 
connected  to  drums,  the  steam  rising  from  the  tubes  and  passing  into 
the  drums,  where  a  steam  space  is  left,  and  the  hot  gases  play  all 
round  the  tubes,  and  the  under  surface  of  the  drums.  The  con- 
struction of  water-tube  boilers  varies  quite  as  much  as  that  of  fire- 
tube  boilers,  but  all  are  on  certain  main  lines.  All  of  them  must 
have,  as  in  the  case  of  fire-tube  boilers,  a  space  sufficient  to  hold  a 
certain  quantity  of  water,  another  space  sufficient  to  hold  a  certain 
quantity  of  steam,  an  arrangement  for  delivering  water  to  the  water 
space,  as  a  portion  is  converted  into  steam,  an  arrangement  for 
carrying  the  steam  away  from  the  steam  space  when  it  is  formed, 
and  when  it  is  to  be  used.  It  must  also  contain  some  arrangement 
for  burning  the  fuel  that  is  to  be  employed  to  furnish  the  heat,  and 
for  directing  the  hot  gases  over  the  tubes  and  the  drums,  in  such  a 
manner  that  all  the  heat  is  extracted  from  them  that  is  not  required 
to  furnish  draught.  The  fuel  is  burned  in  very  much  the  same 
manner  as  in  the  fire-tube  boiler,  though  the  furnaces,  as  will  be 
explained,  are  rather  different,  and  there  is  the  same  problem,  the  hot 
gases  passing  from  the  surface  of  the  burning  fuel  having  a  temperature 


78       STEAM   BOILERS,   ENGINES,    AND    TURBINES 

of  approximately  2400°  F.  and  being  required  to  be  cooled  down 
before  leaving  the  boiler  to  about  600°,  or  where  forced  draught  is 
employed,  to  considerably  less.  The  whole  construction  of  water- 
tube  boilers  necessarily  differs  entirely  from  that  of  fire-tube  boilers, 
in  the  majority  of  forms,  because  the  arrangements  are  quite  different. 
In  the  fire-tube  boilers,  it  will  be  remembered,  there  is  a  shell  holding 
water,  and  hot  gases  are  passed  through  flues,  tubes,  etc.,  piercing 
the  water,  and  round  the  sides  and  bottom  of  the  shell.  In  the 
water-tube  boiler  the  water  is  held  very  largely  in  tubes,  with  drums 
or  cylinders  or  some  similar  arrangement  above,  to  assist  in  the 
circulation,  and  to  form  a  receptacle  for  the  steam.  It  will  be 
understood  that  steam,  when  it  is  formed,  being  so  much  lighter  than 
water,  rises,  and  if  it  is  not  condensed  before  it  reaches  the  surface, 
comes  away  from  the  water,  and  enters  the  space  provided  for  it. 
One  of  the  advantages  claimed  for  the  arrangement  of  the  Lancashire 
boiler,  with  the  hottest  portion  of  the  gases  in  direct  contact  with  a 
small  depth  of  water,  is  the  fact  that  the  steam  formed  there  has  only 
a  short  distance  to  rise  to  the  steam  space.  As  will  be  seen,  in 
the  water-tube  boiler  the  steam  has  frequently  a  very  long  distance 
to  pass  before  entering  the  steam  space,  and  it  may  happen,  and  does, 
that  steam  formed  in  one  part  of  the  boiler,  in  one  part  of  the  tubes, 
may  become  water  again  by  passing  through  a  body  of  water  at  a  com- 
paratively low  temperature.  It  by  no  means  follows  that  this  renders 
the  boiler  inefficient,  inasmuch  as  in  order  that  the  steam  may 
become  water  again,  it  must  give  up  its  latent  heat  to  the  water,  and 
in  doing  so,  must  raise  the  temperature  of  the  water  very  considerably. 
It  will  be  remembered  that  in  dealing  with  the  Lancashire  boiler, 
one  of  the  points  that  was  mentioned  as  of  considerable  importance 
was  the  setting  of  the  boiler,  so  that  it  should  be  well  supported,  but 
without  the  supports  carrying  off  much  heat,  the  supports  being  in 
the  form  of  fire-bricks  moulded  to  a  special  form.  In  the  majority 
of  water-tube  boilers,  though  brickwork  enters  very  largely  into  the 
arrangement,  it  does  not  support  any  portion  of  the  boiler.  A 
favourite  arrangement,  employed  by  the  Babcock  &  Wilcox,  and  by 
the  Stirling  Boiler  Company,  and  others,  is :  A  space  of  rectangular 
section  is  formed  by  iron  pillars  supporting  iron  girders,  the  space 
being  afterwards  closed  in  by  fire-bricks  on  the  inside,  and  glazed 
tiles  on  the  outside,  leaving  spaces  for  the  furnace  doors,  and  the 
doors  required  for  getting  at  the  tubes,  etc.  The  girders  supported 
by  the  pillars  themselves  form  the  supports  for  the  drums,  tubes,  etc., 
and  the  rest  of  the  apparatus,  and  as  girders  and  supporting  pillars 
can  be  multiplied  as  much  as  may  be  desired,  within  certain  limits, 
the  limits  being  the  ability  of  the  supports  to  carry  off  heat,  a  very 
substantial  structure  results,  that  is  largely  independent  of  expansions 
and  contractions,  so  far  as  supports  are  concerned.  The  form  and 


BOILERS  79 

arrangement  of  water-tube  boilers  vary  very  considerably,  as  do 
most  engineering  appliances,  according  to  the  ideas  of  the  inventors 
and  the  manufacturers  who  work  out  the  inventors'  ideas,  but  the 
great  majority  of  them  take  the  form  indicated  above,  in  which  there 
are  one  or  more  drums  occupying  the  upper  portion  of  the  apparatus, 
and  resting  or  supported  by  the  girders,  and  supported  partially  by 
the  brickwork  surrounding  them,  the  space  below  being  occupied 
partly  by  the  tubes,  which  have  various  forms,  and  partly  by  the 
furnace.  The  tubes  are  of  various  forms,  and  various  sizes,  from  very 
small  in  the  Thornycroft  and  Yarrow  torpedo-boat  boilers,  up  to  four 
inches  in  the  Babcock  and  other  boilers  of  the  same  type. 

The  arrangement  for  extracting  the  heat  from  the  hot  gases 
formed  by  the  combustion  of  the  fuel,  is  necessarily  different  from 
that  in  the  Lancashire  and  Cornish  and  multitubular  boilers.  For 
practical  purposes  the  whole  of  the  rectangular  box,  that  usually 
forms  the  lower  portion  of  the  boiler  space,  takes  the  place  of  the 
flues  in  the  fire-tube  boilers.  Instead  of  the  hot  gases  passing 
through  the  different  flues  in  succession,  or  in  series,  as  electrical 
engineers  would  express  it,  they  to  a  certain  extent  find  their  own 
way  between  the  surfaces  of  the  tubes  containing  the  water,  guided 
usually  by  baffles  of  incombustible  material,  arranged  to  give  them 
a  circuitous  path,  and  to  ensure  that  every  part  of  every  tube  shall 
be  licked  by  the  gases  on  their  way  to  the  chimney.  In  some 
forms  of  water-tube  boiler,  particularly  in  such  forms  as  the  Climax, 
described  on  p.  98,  and  two  of  the  forms  of  Messrs.  Thorny  croft's 
boiler,  the  hot  gases  have  simply  to  find  their  way  between  inter- 
stices left  between  pipes  in  which  water  is  circulating,  the  pipes 
being  curved  in  various  forms. 

Nearly  all  forms  of  water- tube  boiler  have  a  mud  drum  placed  at 
the  bottom  of  the  rectangular  space  mentioned,  where  the  boiler  is  of 
the  rectangular  form,  the  mud  drum  having  the  same  office  as  the 
mud  hole  in  Lancashire  boilers,  and  the  mud  drum  described  in 
connection  with  some  forms  of  multitubular  boilers. 


An  Advantage  Claimed  for  Water-tube  Boilers 
with  High  Pressures 

One  reason  for  the  increase  in  the  use  of  water-tube  boilers  during 
recent  years  is  the  increase  of  the  steam  pressures  that  has  been 
referred  to  in  the  first  chapter.  In  the  formulae  given  for  the  work- 
ing pressure  of  boilers  with  different  patterns  of  furnaces  on  p.  65  it 
will  be  remembered  that  the  diameter  of  the  furnace  formed  the 
denominator  of  the  fractions  comprising  the  formula.  A  similar 


8o      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

formula  is  employed  for  the  working  pressure  allowable  with  Cornish 
or  Lancashire  boilers,  for  the  boilers  themselves. 

In  both  formulae  the  working  pressure  allowable  with  any  given 
thickness  of  boiler  plate  and  other  construction  depends  inversely 
upon  the  diameter  of   the  boiler.     The  larger  the  diameter  of  the 
boiler,  the  thicker  must  be  the  steel  plate  of  which  the  boiler  is 
composed  for  a  given    pressure,  and   it   will   easily  be   understood 
that  as  boiler  pressures  increase,  the  sizes  of  the  boilers  must  either 
be  limited  or  the  thickness  of  the  boiler  plate  must   be  increased 
considerably,   and   with   it   the  cost   of  working,   the   cost   of    the 
material   itself,  and   the    efficiency  of   the  boiler  will    be  reduced, 
from  the  fact  that  the  increased  thickness  of  the  plate  will  allow 
only  a  smaller  quantity  of  heat  to  pass  from  the  hot  gases  through 
the    boiler  shell    to  the  water    at  the  sides    and   bottom.     So   far, 
makers  of  Lancashire  boilers  have  had  no  difficulty  in  constructing 
boilers  for  pressures  of  200  Ibs.,  which  is  rather  higher  than  most  steam 
users  care  to  go  at  the  present  time,  except  for  steamships  and  special 
cases.     There  is  also  no  difficulty  whatever  in  arranging  batteries  of 
boilers,  and  this  is  merely  a  continuation  of  the  plan  that  was  neces- 
sarily adopted  in  low-pressure  days,  because,  as  already  explained, 
much  more  steam  was  required  with  low  pressures  than  with  high. 
On  the  other  hand,  there  can  be  no  doubt  that  the  increase  of  steam 
pressures  has  increased  the  strain  upon  the  boiler  shells  in  the  case 
of  the  Lancashire  and  Cornish  boilers.    It  will  be  remembered  that  with 
all  fluids,  liquids,  and  gases  the  pressure  communicated  to  any  part 
of  a  body  of  fluid  is  transmitted  through  the  fluid  equally  in  all 
directions,  and  this  applies  to  the  case  of  the  mixed  fluids,  the  water 
and  steam  in  Lancashire  and  Cornish  boilers.     When  water  only  is  in 
the  boiler,  as  when  it  is  first  filled  up  for  steam  raising,  the  only  pressure 
upon  any  part  is  that  due  to  the  weight  of  the  water.     When  steam 
is  formed,  however,  the  pressure  acquired  by  the  steam  is  transmitted 
through  the  body  of  the  steam  in  the  steam  space  and  through  the 
body  of  the  water  in  the  water  space  to  every  part  of  the  boiler,  and  par- 
ticularly to  the  boiler  shell,  the  pressure  so  transmitted  acting  radially 
upon  the  rings  of  which  the  boiler  is  built  up,  and  tending  to  force 
the  seams  open,  or  to  burst  a  plate  if  there  is  any  flaw  in  it.     The 
pressure  in  pounds  exerted  upon  any  ring  of  the  boiler  is  found  by 
multiplying  the  total  surface  of  the  ring  in  inches  by  the  pressure 
of  the  steam  in  pounds.     Thus,  taking  a  ring  6  feet  in  length  and  a 
boiler  of  8  feet  in  diameter  and  a  steam  pressure  of  200  Ibs.,  the  total 
force  exerted  by  the  steam  tending  to  open  the  joint  of  the  ring,  or  to 
rupture  the  plate  of  which  the  ring  is  formed,  is  found  by  the  formula — 

F=  P  x  D  x  L  x  TT 

where  P  is  the  steam  pressure  in  pounds,  D  is  the  diameter  of  the 


PLATE  4A  — Three-furnace  marine  boiler,  made  by  the  Central  Engineering  Works, 

Hartlepool. 


PLATE   4s. — Thornycroft  water-tube  boilers,  arranged   for  ship  work.     The  steam 
drums  are  seen  at  the  top,  the  furnaces  below,  the  tubes  being  inside  the  casing. 

[To  face  p.  86. 


BOILERS  8 1 

boiler  in  inches,  L  is  the  length  of  the  ring  in  inches.  For  the  case 
mentioned,  P  is  200,  D  is  96,  L  is  72,  and  F  will  therefore  =  about 
188  tons. 

Though  there  is  no  difficulty  whatever  in  providing  material  to 
resist  this  strain,  nor  to  make  joints  in  the  material  of  which  the 
boiler  is  composed  also  to  resist  the  strain,  it  will  be  seen  at  once  that 
if,  as  in  the  case  of  all  water-tube  boilers,  the  largest  diameter  of  any 
vessel  exposed  to  steam  pressures  is  reduced  to,  say,  3  feet  the 
chance  of  rupture  of  the  shells  of  which  the  vessels  are  composed  is 
enormously  reduced,  and  hence  higher  pressures  can  be  employed 
with  greater  confidence  where  boilers  are  in  the  hands  of  men  who 
are  not  always  as  careful  as  they  might  be  ;  and,  again,  it  is  possible 
to  economise  in  the  material  of  which  the  boilers  are  constructed. 

It  will  be  noted  also  that  in  the  water-tube  boiler,  the  major 
portion  of  the  apparatus  is  exposed  to  very  much  smaller  strains 
than  those  to  which  the  larger  portion  of  Cornish  and  Lancashire 
and  multitubular  boilers  are  exposed. 

Convenience  of  Transport  of  Water=tube  Boilers 

Another  undoubted  advantage  that  is  claimed  for  water-tube 
boilers  is  their  great  convenience  for  transport  and  for  fitting-up. 
For  transporting  machinery  to  the  Colonies  or  to  foreign  countries,  it 
is  a  great  convenience  to  be  able  to  take  machines  apart  into  portions 
that  are  handled  and  packed  easily,  and  the  packages  of  which  can 
be  handled  by  the  cranes,  etc.,  on  dock  sides.  It  will  be  seen. from 
the  descriptions  which  follow,  that  water-tube  boilers  render  them- 
selves very  conveniently  to  this :  the  headers,  the  tubes,  the  drums, 
the  furnace,  the  uprights,  the  girders  all  being  able  to  be  taken  apart 
and  remounted  with  the  aid  of  a  proper  plan,  where  they  are  to  be 
used. 

And  there  are  other  cases  even  in  this  country  where  this  con- 
venience is  of  great  service.  In  London  and  many  of  our  large 
towns,  factories  and  establishments,  such  as  hospitals,  hotels,  etc., 
have  grown  up  in  the  middle  of  populous  districts,  and  have  been 
gradually  built  in,  with  the  result  that,  if  it  has  been  necessary  either 
to  fix  boilers  or  change  them  for  larger  ones,  it  has  been  absolutely 
impossible  to  get  in  a  Lancashire  or  Cornish  boiler  without  pulling 
down  a  portion  of  the  wall  of  the  building.  With  the  water- tube 
boiler  the  difficulty  is  very  much  reduced. 

The  Water  Circulation  in  Water-tube  Boilers 

The  question  of  the  circulation  of  water  in  a  boiler  has  been 
dealt  with  generally  in  the  first  chapter,  and  in  connection  with 

G 


82       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

Cornish  and  Lancashire  boilers  on  p.  54.  It  is  claimed  for  water-tube 
boilers  that  their  construction  renders  water  circulation  very  much 
more  easily  accomplished,  and  very  much  more  efficient.  In  all 
forms  of  water-tube  boiler,  as  will  be  seen  from  the  descriptions 
which  follow,  a  certain  portion  of  the  tubes  in  which  the  water  lies  is 
exposed  to  the  hottest  portion  of  the  hot  gases,  other  portions  of  the 
tubes  being  exposed  to  cooler  parts  of  the  gases,  and  still  other  parts 
to  still  colder  portions  ;  the  result  being  that  there  is  a  considerable 
difference  in  the  quantity  of  heat  transmitted  through  the  tubes  to 
the  water  lying  in  them  in  one  part  of  the  bank  of  tubes  than  in 
the  others,  this  leading  to  the  greater  expansion  of  the  water  in  that 
portion  of  the  tubes,  and  therefore  to  the  rise  of  the  water  exposed  to 
the  greater  heat,  its  place  being  taken  by  water  from  the  part  exposed 
to  a  cooler  portion  of  the  gases,  which  in  its  turn  has  been  forced  away 
by  heat  from  its  own  place,  and  so  on,  the  result  being  a  continuous 
motion  of  the  water  through  the  tubes  and  through  the  drums  on  the 
top  provided  for  it. 


The  Furnace  of  Water-tube  Boilers 

Practically  the  whole  of  the  space  under  the  lowest  bank  of  tubes 
in  the  front  portion  of  the  rectangular  space  enclosed  by  the  brick 
walls  described  forms  the  furnace,  the  whole  width  being  filled  with 
fire-bars  extending  from  front  to  back  for  the  usual  distance  (about 
6  feet),  the  bars  being  supported  in  the  centre  of  their  length  in 
the  usual  way.  The  fire-bars  form  a  platform  for  the  fuel,  extending 
the  whole  width  of  the  boiler.  There  must  be  one  or  two  furnace 
doors  and  one  or  two  ash-pit  doors,  as  shown  in  the  various  drawings. 


Forms  of  Water-tube  Boilers 

The  Babcock.— As  mentioned  above,  the  forms  of  water-tube 
boilers  are  very  numerous.  The  Babcock  and  Wilcox  boiler  is  one 
of  those  best  known  in  this  country  and  in  America.  It  is  shown  in 
section  in  Plate  5A,  and,  as  will  be  seen,  it  comprises  a  number 
of  tubes,  usually  of  about  4  inches  in  diameter,  arranged  at  an  angle 
of  30°  with  the  horizontal,  the  tubes  sloping  downwards  from  the 
front  towards  the  back  of  the  boiler.  The  tubes  are  arranged  in 
vertical  banks,  each  of  a  certain  number,  eight  being  a  favourite,  and 
a  certain  number  of  vertical  rows  are  arranged  side  by  side,  according 
to  the  work  the  boiler  is  to  perform.  At  the  front  and  back  of  the 
boiler  the  tubes  are  expanded  into  what  are  termed  headers,  which 
are  practically  boxes  arranged  to  enable  the  tubes  to  be  reached  for 


U  N  I  V  E  R  S 

or 

BOILERS  83 

cleaning,  and  which  also  receive  the  steam  from  the  tubes,  and  the 
water  from  the  drum  above,  conveying  the  steam  to  the  drum,  and 
the  water  back  to  the  tubes.  The  headers  are  fixed  at  right  angles 
to  the  tubes,  the  front  headers  being  connected  by  short  tubes  with 
the  under  side  of  the  steam  drum,  the  back  headers  being  also  con- 
nected with  the  rear  part  of  the  steam  drum  by  long  tubes,  as  shown. 
The  steam  drum  or  drums  (there  are  more  than  one  for  large  sizes  of 
boilers)  are  placed  longitudinally  over  the  tubes,  and  the  circulation 
of  the  water  and  steam  is,  from  the  front  end  of  the  tubes  through 
the  front  headers  to  the  steam  drum,  through  the  water  in  the  steam 
drum  to  the  tubes  leading  to  the  back  headers,  and  thence  to  the 
back  headers  and  the  tubes  again. 

The  rectangular  space  forming  the  furnace  and  combustion 
chamber  is  divided  by  a  fire  bridge  of  fire-brick  at  the  back  of  the 
furnace,  somewhat  similar  to  the  usual  bridge  at  the  back  of  the 
furnace  of  Lancashire  and  Cornish  boilers,  but  the  bridge  is  extended 
upwards  to  a  rather  greater  height  than  is  usual  in  Lancashire  and 
Cornish  boilers,  and  from  its  top  a  fire-brick  baffle  extends  through 
the  nest  of  tubes,  being  fixed  at  right  angles  to  them,  to  the  under 
side  of  the  steam  drum,  or,  where  one  is  used,  to  the  under  side  of 
the  superheater,  as  will  be  explained  later.  At  the  back  of  the 
rectangular  space,  as  will  be  seen  from  Plate  5 A,  the  bottom  header 
is  met  by  a  fire-brick  bridge  and  baffle,  and  there  is  a  third  fire- 
brick baffle  about  halfway  between  that,  connected  to  the  furnace 
bridge  and  the  back  headers.  From  the  illustration  it  will  be  seen 
that  the  front  portion  of  the  tubes,  comprising  half  their  length,  is 
exposed  to  the  radiation  from  the  glowing  fuel  on  the  grate-bars, 
and  to  the  hot  gases  at  their  highest  temperature.  It  will  be 
understood  that  the  hot  gases  thread  themselves  between  the  tubes, 
licking  round  the  tubes  as  flames  do,  then  passing  upwards  to  the 
lower  part  of  the  steam  drum,  down  over  the  portion  of  the  tubes 
between  the  two  middle  baffles,  up  through  the  rear  portion  of  the 
tubes,  across  the  back  headers,  and  the  tubes  connecting  them 
to  the  boilers,  and  thence  down  to  the  flue  leading  to  the 
chimney. 

Where  a  superheater  is  employed  of  the  Babcock  and  Wilcox 
type,  as  seen  in  Plate  5A,  it  is  fixed  in  the  upper  portion  of  the 
rectangular  space  forming  the  heating  chamber,  and  receives  the 
hot  gases  as  they  pass.  The  Babcock  and  Wilcox  Company  also 
manufacture  a  special  form  of  their  water-tube  boiler  for  use  on 
board  ship.  The  principal  difference  between  the  marine  type  of 
Babcock  boiler  and  the  land  type  is  really  the  form  and  arrangement 
of  the  tubes.  They  are  arranged  as  in  the  other  boiler,  at  a  slight 
inclination  with  the  vertical,  but  there  are  a  very  much  larger  number 
of  them ;  they  are  smaller,  and  fixed  very  much  more  closely  together. 


84       STEAM   BOILERS,   ENGINES,   AND   TURBINES 

In  fact,  the  arrangement  reproduces  the  multitubular  marine  type 
boiler  described  on  p.  70,  but  with  the  tubes  arranged  to  hold  the 
water,  and  with  the  hot  gases  playing  around  them,  in  place  of  as  in 
the  fire-tube  boiler,  the  gases  passing  through  the  tubes,  and  the  water 
being  round  them.  The  steam  drum  is  fixed  directly  above  the  tubes, 
connected  to  the  front  headers  by  very  short  tubes,  and  to  the  back 
headers  by  longer  ones,  the  drum  itself  being  fixed  at  right  angles 
to  the  line  of  the  tubes,  instead  of  parallel  with  them.  As  on  board 
ship,  it  is  not  convenient  to  have  brickwork  in  the  same  manner  as 
on  shore ;  the  sides  of  the  furnace  only  are  lined  with  fire  brick,  and 
the  whole  structure  is  surrounded  by  a  removable  wrought-iron 
casing. 

The  Stirling  Water=tube  Boiler 

In  the  Stirling  water-tube  boiler  the  tubes  are  arranged  very 
differently  from  the  Babcock.  Longitudinal  and  transverse  sections 
of  the  boiler  are  shown  in  Fig.  12.  There  is  the  same  arrangement 
for  supporting  the  drums  and  tubes,  and  the  same  rectangular 
heating  chamber ;  but  the  tubes,  which  are  in  three  separate  banks, 
are  fixed  at  a  very  different  angle  to  those  in  the  Babcock  boiler. 
There  is  one  drum,  the  mud  drum  referred  to  above,  fixed  at  the 
back  of  the  boiler,  and  the  three  banks  of  tubes  are  fixed  between 
the  three  drums  above,  and  the  mud  drum  below.  This  necessarily 
leads  to  the  inclination  of  the  different  banks  of  tubes  with  the 
vertical,  being  different.  As  will  be  noticed  from  the  drawing,  the 
rear  bank  is  very  nearly  vertical,  and  its  tubes  are  curved  round 
slightly  towards  the  bottom,  to  enable  them  to  enter  the  mud  drum 
in  a  convenient  manner.  This  bank  of  tubes  is  fixed  between  the 
rear  drum  above  and  the  mud  drum.  The  next  bank  of  tubes  is 
fixed  between  the  middle  drum  above  and  the  mud  drum,  and  is 
slightly  more  inclined  with  the  vertical,  its  lower  ends  also  being 
slightly  curved,  where  they  enter  the  mud  drum.  The  front  bank 
of  tubes  is  still  more  inclined  to  the  vertical,  and  connects  the  front 
upper  drum  with  the  mud  drum.  The  furnace  is  fixed  in  the 
front,  in  a  similar  position  to  that  in  the  Babcock  boiler.  There 
is  only  a  small  bridge  at  the  back  of  the  furnace,  but  there  is  a  roof 
of  fire-brick  over  the  front  of  the  furnace,  and  extending  for  three- 
quarters  of  the  length  of  the  furnace  bars,  this  roof  tending  to  form 
a  combustion  chamber.  As  in  the  Babcock  and  other  water-tube 
boilers,  there  are  fire-brick  baffles  fixed  in  the  Stirling  boiler,  arranged 
to  direct  the  course  of  the  hot  gases  over  the  whole  length  of  the 
tubes  before  passing  to  the  chimney.  There  is  a  baffle  behind  the 
front  bank  of  tubes,  extending  for  three-quarters  of  their  length 
from  the  mud  drum  upwards,  so  that  the  hot  gases  are  obliged 


r 


86       STEAM   BOILERS,   ENGINES,   AND    TURBINES 

to  pass  longitudinally  along  the  tubes  until  they  reach  nearly  to  the 
front  steam  drum. 

The  second  bank  of  tubes  have  a  baffle  fixed  behind  them, 
extending  from  the  middle  steam  drum  downwards  for  three  parts 
of  their  length,  so  that  the  hot  gases,  after  passing  through  the  length 
of  the  front  bank,  pass  across  to  the  top  of  the  second  bank,  longi- 
tudinally down  their  full  length,  and  thence  across  to  the  rear  bank. 
The  rear  bank  is  protected  partly  by  a  fire-brick  wall,  forming  part 
of  the  flue  leading  to  the  chimney,  and  partly  by  a  baffle  fixed  behind 
them,  extending  upwards  for  about  three  parts  of  their  length,  the 
hot  gases  therefore  being  obliged  to  pass  along  the  rear  bank  longi- 
tudinally, and  thence  passing  into  the  space  that  will  be  seen  behind 
them,  and  downwards  to  the  chimney  flue.  There  is  the  same 
arrangement  in  the  Stirling  boiler  for  making  the  boiler  of  any 
capacity  up  to  a  certain  size.  The  tubes  are  arranged  in  rows  or 
stacks,  of  a  certain  number,  six  or  eight,  reckoning  from  front  to 
back,  and  as  many  vertical  rows  are  fixed  side  by  side  as  may  be 
required  for  the  evaporation  the  boiler  is  to  furnish.  The  Stirling 
Boiler  Company  also  provide  a  superheater,  which  is  fixed,  as  will 
be  seen  in  the  drawing,  between  the  two  front  banks  of  tubes,  a 
baffle  below  the  lower  end  of  the  superheater  ensuring  that  the  hot 
gases  pass  over  the  superheater  tubes. 

The  drums  of  the  Stirling  boiler  are  all  fixed  at  right  angles  to 
the  front  of  the  boiler,  as  shown  in  Fig.  12.  The  three  upper  drums 
have  their  steam  spaces  connected  by  pipes,  as  shown,  and  the  two 
foremost  drums  have  their  water  spaces  connected  by  tubes. 

The  feed  water  is  supplied  to  the  rear  drum,  and  it  is  claimed  by 
the  Stirling  Company  that  the  vertical  arrangement  of  the  rear  tubes, 
and  the  fact  that  they  are  subject  to  the  gases  at  comparatively  low 
temperature,  heats  the  water  sufficiently  to  allow  it  to  deposit  any 
foreign  substances  in  the  mud  drum  at 'the  bottom,  from  which  it  can 
be  removed  by  the  pipe  shown  in  the  drawing.  The  circulation  of 
the  water  then  is  from  the  rear  steam  drum,  downwards  to  the  mud 
drum,  upwards  through  the  two  banks  of  tubes  to  the  two  upper 
drums.  It  will  be  noticed  that  the  rear  drum  and  the  front  drum 
are  shown  as  having  a  greater  depth  of  water  than  the  middle  drum. 
It  is  from  the  middle  drum  that  the  steam  is  taken.  On  the  other 
hand,  the  front  bank  of  tubes  receive  the  greatest  amount  of  heat, 
and  it  may  be  supposed  that  the  largest  portion  of  the  steam  is 
produced  in  them,  the  steam  bubbles  rising  through  the  water  in  the 
tubes,  into  the  water  in  the  front  drum,  thence  passing  into  the  steam 
space  in  the  front  drum,  and  thence  by  the  connecting  pipe  to  the 
steam  space  of  the  middle  drum.  Steam  is  also  produced  in  the  middle 
bank  of  tubes,  and  takes  its  course  through  the  length  of  the  tubes 
and  the  water  in  the  bottom  of  the  middle  drum  to  its  steam  space. 


BOILERS  87 


The  Nesdrum  Water=tube  Boiler 

This  boiler,  made  by  Messrs.  Kichardson,  Westgarth  &  Co., 
presents  several  novel  features,  but  the  main  principles  of  its  con- 
struction are  the  same  as  those  of  the  boilers  already  described. 
There  is  the  same  rectangular  space  enclosed  by  fire-brick  and  glazed 
bricks,  built  in  round  the  boiler  tubes  and  drums,  the  steam  drum 
and  the  banks  of  tubes  to  be  described  being  supported  by  a  girder, 
fixed  on  iron  pillars,  as  in  the  other  forms  of  boiler.  There  is  only 
one  steam  drum,  and  there  are  three  or  four  banks  of  tubes,  according 
to  the  size  of  the  boiler.  But  the  banks  or  nests  of  tubes  are  arranged 
in  a  peculiar  manner :  several  tubes  of  a  given  diameter  are  expanded 
into  cylindrical  headers,  which  are  really  small  drums.  There  is  one 
nest  of  tubes  standing  vertically  at  the  back  of  the  boiler,  with  a 
comparatively  large  cylinder  at  its  top  and  bottom.  Near  the  front 
of  the  boiler  are  two  or  three  nests  of  tubes,  according  to  the  size  of 
the  boiler,  each  having  a  large  header  cylinder  at  the  top,  and  a  small 
one  at  the  bottom.  These  two  or  three  nests  are  arranged  parallel 
with  each  other,  and  slightly  inclined  to  the  vertical.  The  steam 
drum  proper  is  fixed  between  the  upper  header  of  the  rear  bank  of 
tubes,  and  that  of  the  rear  of  the  three  front  banks.  The  steam  drum 
itself  and  the  upper  cylinders  of  the  banks  of  tubes,  all  act  as  steam 
drums.  They  are  all  usually  filled  partly  with  water  and  partly  with 
steam.  They  all  have  their  steam  and  water  spaces  connected  together 
by  pipes.  The  banks  of  tubes  are  protected  by  fire-brick  baffles,  in 
a  similar  manner  to  those  of  the  Stirling  boiler,  the  front  bank  having 
a  baffle  behind  the  tubes,  extending  from  the  rear  header  about  two- 
thirds  of  the  length  of  the  tubes.  The  next  bank  has  a  baffle  behind 
its  tubes,  extending  from  the  upper  header  about  halfway  down  the 
length  of  the  tubes ;  the  third  bank,  where  there  is  one,  has  a  baffle 
behind  its  tubes,  extending  from  the  lower  header  about  two-thirds 
of  its  length.  There  is  a  horizontal  baffle  between  the  top  of  the 
baffle  on  the  third  bank,  meeting  the  rear  vertical  bank  about  one- 
third  of  the  way  down.  Where  there  are  only  two  front  banks  of 
tubes,  a  baffle  is  carried  from  between  the  bottom  headers  of  the 
rear  vertical  bank,  and  the  second  inclined  bank  upwards,  and  then 
horizontally  to  meet  the  vertical  bank,  at  about  one-third  of  its 
length  from  the  top.  There  is  another  baffle  fixed  horizontally 
behind  the  rear  vertical  bank  of  tubes,  and  there  is  yet  another 
baffle  in  front  of  the  lower  part  of  the  rear  bank  of  tubes. 

The  furnace  is  fixed  in  the  front  of  the  boiler,  as  in  the  other 
cases.  There  is  a  low  fire-brick  bridge  at  the  back  of  the  furnace 
bars,  and  the  hot  gases  pass  up  the  front  of  the  front  bank  of  tubes, 
curl  over  the  upper  portion  of  the  front  bank,  down  between  the 


88      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

two  front  banks,  across  the  body  of  the  second  bank,  up  between 
the  second  and  third  banks,  where  there  is  a  third  bank,  across  the 
body  of  the  top  of  the  third  bank,  across  the  body  of  the  top  of  the 
rear  bank,  back  into  the  body  of  the  rear  bank,  and  vertically  down- 
wards along  the  rear  bank  to  the  flues. 

A  superheater  is  fixed  in  the  heating  chamber,  between  the  rear 
bank  of  tubes  and  the  last  of  the  inclined  banks.  The  boiler  is  also 
arranged  on  the  same  lines  as  the  Babcock,  Stirling,  and  others,  to 
be  built  up  to  any  size  within  certain  limits,  by  fixing  two  or  more 
nests  in  each  row,  side  by  side. 

The  bottom  header  of  the  rear  bank  acts  as  the  mud  drum  for 
the  boiler,  the  feed  water  being  supplied  to  the  upper  header  of  the 
same  bank,  and  the  circulation  being  very  much  as  in  the  Stirling. 
The  water  passes  first  down  the  rear  bank  of  tubes,  then  from  the 
rear  header  to  the  other  lower  headers,  and  from  them  up  the  inclined 
banks  to  their  headers,  as  it  is  formed,  passing  up  through  the  water 
into  the  steam  spaces  in  each  header,  and  thence  to  the  steam  space 
in  the  steam  drum.  Circulation  of  the  water  in  all  of  these  forms 
of  boiler  is  from  the  water  in  the  steam  drum,  and  through  the  tubes 
as  explained,  round  and  round.  The  steam  drum  in  the  Nesdrum 
boiler  is  fixed  at  right  angles  to  the  line  of  the  front  of  the  boiler. 


The  Woodeson  Water=tube  Boiler 

This  boiler,  which  is  made  by  Messrs.  Clarke,  Chapman  &  Co., 
of  Gateshead,  is  somewhat  similar  to  the  Nesdrum.  There  are  three 
drums  above,  and  three  below,  the  upper  drums  being  the  steam 
drums,  and  the  lower  water  drums,  and  the  three  pairs  of  drums  are 
connected,  as  shown,  by  banks  of  tubes,  the  tubes  connecting  the 
rear  drums  being  vertical,  those  connecting  the  middle  drums  a  little 
inclined  to  the  vertical,  and  those  connecting  the  front  drums  still 
more  inclined.  The  three  upper  drums  are  connected  by  cross  tubes 
as  shown,  in  the  steam  and  water  spaces,  and  the  three  lower 
drums  are  also  connected  by  cross  tubes.  The  drums  are  all  fixed 
at  right  angles  to  the  line  of  the  boiler  front.  There  is  a  steam 
dome  or  receiver  fixed  above  the  upper  drums,  and  it  is  from  this 
that  the  steam  is  taken.  The  arrangement  of  the  masonry,  etc.,  is 
very  similar  to  that  of  the  boilers  that  have  been  described,  iron 
girders  standing  upon  iron  uprights  supporting  the  upper  drums, 
upon  which  they  rest,  and  the  lower  drums  being  supported  by  the 
tubes  to  which  they  are  connected,  the  rectangular  space  formed  by 
the  uprights  and  girders  being  built  in  with  fire-brick  in  the  usual 
way,  the  steam  drums  standing  above.  The  furnace  occupies  its 
usual  position  in  front,  and  there  are  baffles  behind  the  tubes, 


PLATE  5A. — Babcock  and  Wilcox  Boiler,  with  Chain  Grate.  Stoker  and  Superheater, 
with  brickwork  removed  to  show  the  Tubes,  Furnace,  etc. 


PLATE  SB. — Water-tube   Boiler  made  by  Messrs.  Marshall,  with  a  portion  of  the 
enclosing  brickwork  removed  to  show  the  Tubes. 

[To  face  p.  88. 


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90      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

arranged  to  direct  the  course  of  the  hot  gases  over  the  tubes  and  the 
under  side  of  the  drums  in  succession.  The  boiler  is  shown  in 
section  in  Fig.  13.  The  superheater,  when  employed,  is  fixed  between 
the  rear  banks  of  tubes,  and  is  of  the  form  shown. 

The  groups  of  tubes  are  expanded  into  flat  discs,  which  form 
part  of  the  upper  side  of  the  mud  drums,  and  the  lower  side  of 
the  steam  drums,  and  above  the  steam  drums  are  arranged  hand 
holes,  by  which  any  of  the  tubes  may  be  reached.  The  feed  water 
is  carried  into  the  rear  steam  drum,  and  passes  down  the  bank  of 
tubes  to  the  rear  mud  drum. 

It  is  claimed  that  the  large  area  of  the  mud  drums  ensure  the 
complete  removal  of  foreign  matter  from  the  water  in  the  boiler. 

It  will  be  noticed  also  that  in  this  form  of  boiler,  provision  is 
made  for  expansion  and  contraction,  by  the  fact  that  the  lower  drums 
are  free  to  move  in  any  direction. 


Water=tube  Boilers  with   Horizontal,   or  Nearly 
Horizontal  Tubes 

There  are  a  number  of  forms  of  water-tube  boilers  on  the  market, 
in  which  the  tubes  are  horizontal,  or  nearly  so.  The  general  con- 
struction of  all  of  them  is  very  much  on  the  lines  of  that  of  the 
Babcock-Wilcox,  but  each  one  of  them  has  some  special  feature  of 
its  own,  for  which  special  advantages  are  claimed.  There  are  two 
portions  of  the  apparatus  in  which  the  different  forms  of  this  type  of 
boiler  differ  from  each  other,  and  from  the  Babcock,  viz.  in  the  form 
and  arrangement  of  the  headers,  and  in  the  course  of  the  hot  gases  over 
the  tubes.  In  all  forms  of  this  type  of  boiler,  and  practically  in  all 
forms  of  water-tube  boiler,  the  tubes  are  stagrgered,  that  is  to  say, 
alternate  tubes  of  the  same  vertical  row  are  slightly  displaced  to  the 
right  or  left,  so  that  the  gases  have  an  easy  passage  between  them, 
and  between  the  successive  horizontal  rows.  This  arrangement,  it 
will  be  seen,  necessitates  a  special  method  of  connecting  the  tubes 
at  the  headers.  In  the  Babcock-Wilcox,  the  headers  of  each  vertical 
row  of  tubes  is  separated  from  the  remainder,  the  header  itself  being 
curved  to  meet  this  requirement.  In  several  of  the  other  forms 
of  this  type  of  boiler,  the  headers,  both  back  and  front,  are  formed 
into  one  water  leg,  as  it  is  termed.  Practically  the  headers  in 
these  cases  are  formed  of  boxes  and  tanks,  closed  at  the  bottom,  and 
opening  at  the  top  into  the  steam  drum,  the  tubes  being  expanded 
into  one  side  of  them.  It  should  be  mentioned,  en  passant,  that 
in  all  these  forms  of  boiler,  arrangements  are  made  for  getting  at 
each  individual  tube  easily,  for  cleaning,  or  for  plugging  up  in  case 
of  the  tube  being  damaged.  For  this  purpose  the  outside  covers  and 


BOILERS  91 

the  headings,  the  covers  away  from  the  tubes,  are  all  pierced  with 
holes  opposite  to  each  tube,  the  holes  being  closed  by  means  of 
various  forms  of  covers,  plugs,  etc.,  that  are  easily  removed,  when 
the  tube  is  to  be  got  at. 

In  the  Babcock  header  hand  holes  are  made  in  each  header,  as 
shown,  and  in  the  other  forms,  where  there  is  a  water  leg,  they  are 
made  in  the  side  of  the  tank  forming  the  water  leg. 


Marshall's  Water-tube  Boiler 

Messrs.  Marshall  &  Sons  of  Gainsborough  make  a  water-tube 
boiler,  shown  in  Plate  OB,  in  which  it  will  be  seen  the  steam 
drum  is  fixed  parallel  with  the  tubes,  both  being  slightly  inclined  to 
the  horizontal.  There  are  water  legs  at  each  end,  into  which  the 
tubes  are  expanded,  as  explained  on  p.  90,  riveted  at  the  top  end 
to  the  steam  drums,  openings  being  cut  in  the  drum  to  provide  for 
the  connection,  the  joint  being  strengthened  with  plates  on  either 
side,  on  the  lines  of  the  butt  joint  described  in  connection  with  the 
Lancashire  boiler.  The  front  and  back  plates  of  each  of  the  water 
legs  are  tied  together  by  hollow  steel  screwed  stays,  the  tubes  formed 
by  these  stays  being  employed  when  the  boiler  is  fixed  in  its  place, 
for  inserting  a  steam  jet  pipe  to  clean  off  the  soot  from  the  outside 
of  the  tubes.  The  furnace  of  the  boiler  is  arranged  for  burning 
practically  any  kind  of  fuel.  The  tubes  are  of  solid  drawn  steel. 
The  course  of  the  hot  gases  is  as  follows.  There  is  a  fire-brick  arch 
under  the  lower  bank  of  tubes,  over  the  furnace,  the  arch  extending 
to  a  little  beyond  the  fire  bridge.  There  are  baffles  also  above  the 
upper  row  of  tubes,  extending  from  the  back  header,  three-quarters 
of  the  way  to  the  front  header.  The  hot  gases  pass  from  the  furnace 
over  the  fire  bridge,  up  over  the  rear  end  of  the  tubes,  along  the  tubes 
longitudinally  from  back  to  front,  over  the  front  end  of  the  upper 
tubes,  along  the  under  side  of  the  steam  drum,  and  from  the  rear  of 
the  steam  drum  by  a  down-take  flue  to  the  chimney. 


Davey,  Paxman's  Water-tube  Boiler 

Messrs.  Davey,  Paxman  &  Co.'s  water-tube  boiler  has  two  sets 
of  tubes,  the  under  set  inclined  slightly  to  the  horizontal,  and 
dipping  away  from  the  front  end,  the  upper  set  inclined  also  slightly, 
but  rising  from  the  front  end.  The  headers  are  in  the  form  of  water 
legs,  the  back  header  being  longer  in  a  vertical  than  the  front  header, 
and  both  are  connected  directly  to  the  steam  drum,  very  much  in 
the  same  way  as  Marshall's.  There  is  also  a  mud  drum  at  the  rear 


92      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

of  the  boiler,  to  which  a  circulating  tube  is  carried  from  the  steam 
drum.  The  tubes  are  solid  welded,  and  there  are  the  usual  hand 
holes  in  the  headers  opposite  each  tube,  the  covers  of  the  hand  holes 
being  made  with  Messrs.  Davey,  Paxman's  metallic  joint. 


The  Wood  Water=tube  Boiler 

This  boiler  is  made  by  Messrs.  Allis,  Chalmers  &  Company  in 
America,  and   Messrs.   Eraser  &  Chalmers  in  this   country.      The 

steam  drum  is  fixed 
parallel  with  the  axis 
of  the  tubes.  The 
arrangement  of  the 
tubes  and  headers  pre- 
sent some  special  fea- 
tures. They  are  shown 
in  Fig.  14.  The  ar- 
rangement of  the  tubes 
and  headers  is  some- 
what similar  to  those 
of  the  Nesdrum  and 
Woodeson  boilers,  but 
there  are  a  very  much 
larger  number  of  tubes 
in  a  nest,  and  the  tubes 
and  their  headers  are 
arranged  slightly  out 
of  the  horizontal,  in- 
stead of  slightly  out 
of  the  vertical,  as  in 
the  Nesdrum.  The 
headers  in  the  Wood 
boiler  are  in  the  form 
of  short  cylinders  with 
dished  outer  ends,  the 
tubes  being  expanded 
into  the  inner  ends, 
as  in  other  forms,  the 

FIG.  14.— Showing  a  portion  of  the  "  Wood  "  Water-tube  front  header  having 
Boiler,  made  by  Messrs.  Eraser  and  Chalmers,  with  hand  holes  in  the 
part  of  the  Brickwork  and  of  the  Header  cut  away.  ^isne(J  surface  There 

is   also  a  manhole  in 

the  centre  of  the  front  header,  11 J  inches  by  15  inches.     The  hand 
holes  are  arranged,  not  one  for  each  tube,  but  so  that  several  tubes  can 


BOILERS  93 

be  reached  from  each  hole.  The  holes  are  elliptical  in  shape.  The 
tubes  with  their  headers  forming  a  complete  vessel,  are  inclined  a  little 
out  of  the  horizontal,  dipping  away  from  the  front,  and  connection 
is  made  with  the  steam  drum  by  large  pipes  at  the  back  and  front. 
The  course  of  the  hot  gases  in  this  boiler  is  a  little  out  of  the  usual. 
The  tubes  are  surmounted  by  a  brick  arch,  and  the  bridge  at  the 
back  of  the  furnace  extends  close  up  to  the  bottom  row  of  tubes, 
and  the  front  of  the  bridge  is  slightly  inclined.  The  hot  gases  pass 
from  the  furnace  up  over  the  front  portion  of  the  tubes,  which  are 
immediately  above  the  back  of  the  furnace,  then  longitudinally  along 
the  tubes,  then  they  pass  around  the  under  side  of  the  back  header, 
the  baffle  preventing  the  gases  from  escaping  at  that  point,  thence 
they  pass  up  round  the  back  of  the  back  header,  along  the  under 
side  of  the  steam  drum,  through  a  flue  at  the  front  end  of  the  steam 
drum,  along  the  flue  shown  above  the  drum,  and  thence  to  the 
chimney. 


The  Galloway  Water=tube  Boiler 

Messrs.  Galloways  make  a  water-tube  boiler  in  which  the  steam 
drum  runs  parallel  from  front  to  back,  and  the  tubes  are  slightly 
inclined  to  the  horizontal.  The  headers  at  front  and  back  are 
divided  into  sections,  each  section  taking  two  sets  of  tubes,  each 
of  the  sections  of  the  headers  being  connected  with  the  steam  drum 
by  two  sets  of  tubes.  Special  cross  boxes  are  provided  for  the 
headers. 


American  Boilers  with  Straight,  or  Nearly 
Straight,   Horizontal  Tubes 

There  are  several  forms  of  boiler  made  in  America,  in  which  the 
tubes  are  nearly  horizontal,  and  each  of  which  has  some  special 
features  of  its  own. 


The  Atlas  Water-tube  Boiler 

In  the  Atlas  boiler,  which  is  shown  in  Plate  6A,  the  tubes  dip 
slightly  from  the  front  to  the  rear  of  the  boiler,  and  the  headers  are 
the  water  legs,  or  tanks,  that  have  been  described  on  p.  90.  The 
special  feature  of  the  boiler  is  the  three  drums  shown  in  the  figure. 
The  drum  at  the  rear  of  the  boiler  receives  the  feed  water,  and,  it  is 
claimed,  purifies  it,  as  explained  below,  extracting  all  foreign  matter, 


94      STEAM    BOILERS,   ENGINES,   AND   TURBINES 

and  thereby  rendering  the  mud  drum  provided  in  other  boilers, 
unnecessary.  The  front  drum  corresponds  to  the  steam  drum  usually 
carried  by  water-tube  boilers,  but  there  is  a  third  drum,  shown 
between  the  other  two,  and  which  is  slightly  smaller,  and  which  is 
the  steam  drum  proper.  In  addition,  as  will  be  seen  from  the  illus- 
tration, there  are  another  set  of  tubes  connecting  the  front  and  rear 
drums,  and  there  is  a  third  set  of  tubes  connecting  the  front  drum 
and  the  middle  drum,  and  a  fourth  set,  short  tubes,  connecting  the 
middle  drum  with  the  rear  drum.  The  lower  tubes,  which  are 
expanded  into  the  inner  plates  of  the  water  legs  in  the  usual  way, 
are  the  steam  generators  proper,  and  the  hot  gases  are  directed  over 
successive  sections  of  them  by  vertical  baffles,  very  much  as  in  the 
Babcock,  the  front  ends  of  the  tubes  receiving  the  first  lot  of  hot 
gases  which  pass  over  and  down  over  a  middle  section,  and  then 
upwards  again,  and  over  a  rear  section.  In  addition  to  this,  how- 
ever, the  hot  gases  pass  upwards  to  the  upper  set  of  tubes,  on  the 
upper  side  of  which  are  fire-brick  baffles,  enclosed  by  masonry.  The 
tubes  connecting  the  front  and  rear  drums  are  merely  for  circulating 
the  water.  The  water  in  the  front  portion  of  the  lower  tubes  being 
heated,  expands,  some  of  it  forming  steam,  the  steam  and  water 
passing  into  the  front  header,  and  thence  into  the  front  drum,  where 
the  steam  is  separated,  rising  into  the  steam  space,  which  should 
occupy  about  half  the  area  of  the  drum.  The  water  passes  on 
through  the  horizontal  tubes  to  the  rear  drum,  where  it  meets  the 
feed  water,  and  passes  down  through  the  rear  header,  entering  the 
back  of  the  generating  tubes,  and  from  thence  commencing  its 
passage  again.  A  phenomenon  is  worth  noting  here,  that  is  common 
to  all  of  the  water- tube  boilers,  with  tubes  arranged  in  this  manner, 
and  with  the  hot  gases  passing  over  the  tubes  in  sections,  viz. : — 
that  the  water  entering  the  tubes  meets  first  the  colder  gases, 
and  has  its  temperature  raised  to  a  certain  degree,  then  passing 
on  to  the  next  section,  its  temperature  is  still  further  raised,  and 
then  passing  on  to  the  front  section  it  receives  the  full  force  of  the 
hottest  gases.  This  is  in  accordance  with  the  latest  modern  practice, 
wherever  heat  is  to  be  transferred  from  water  to  gas,  from  gas  to  air, 
from  water  to  water,  etc.,  either  in  raising  steam,  in  condensing,  in 
heating  air,  in  cooling  air,  or  in  any  other  change.  The  hottest 
portion  of  the  substance  receiving  heat,  or  from  which  heat  is  being 
extracted,  is  always  nearest  the  hottest  portion  of  the  substance  from 
which  it  is  to  receive  heat,  or  to  which  it  is  to  deliver  heat. 

The  steam  separated  from  the  water  in  the  front  drum,  passes 
along  the  upper  range  of  tubes  to  the  steam  drum  proper,  and  it  is 
claimed  that  in  this  bank  of  tubes  the  steam  is  subject  to  super- 
heating and  drying,  and  that  the  boiler  thence  supplies  perfectly  dry 
steam.  The  amount  of  superheat  is  not  great,  from  10°  to  30°,  but 


BOILERS  95 

it  is  claimed  that  it  is  sufficient  to  dry  the  steam.  Any  water 
remaining  in  the  steam,  it  is  intended  should  pass  by  the  tubes 
shown,  from  the  middle  drum  to  the  rear  drum. 


The  Water- Purifying  Apparatus  of  the  Atlas 

Boiler 

The  water-purifying  apparatus  of  this  boiler  is  worth  separate 
notice.  As  mentioned  above,  it  is  claimed  that  the  apparatus 
separates  foreign  substances,  that  will  afterwards  deposit  on  the  inside 
of  the  tubes,  from  the  water  before  it  leaves  the  rear  drum.  The 
purifier  consists  of  a  semi-conical  vessel  with  closed  ends,  but  with 
open  top.  The  feed-water  pipe  discharges  into  one  end  of  the 
purifier,  and  at  the  other  end  there  is  a  blow-off  cock,  to  the  outside 
of  the  boiler.  The  purifier  vessel  is  immersed  in  the  water  contained 
in  the  rear  drum,  and  is  supported  from  the  upper  portion  of  the 
drum  by  loose  straps.  It  is  claimed  that  the  water  in  the  purifier 
being  subject  to  the  heat  of  the  water  and  steam  in  the  rear  drum, 
has  its  temperature  raised  to  from  250°  to  275°  F.,  while  in  the 
purifier,  and  that  it  is  gradually  caused  to  overflow  from  the  purifier 
vessel,  at  the  end  near  which  it  entered  at  this  temperature,  it  then 
passing  down  with  the  water  already  in  the  rear  drum  into  the  rear 
water  leg,  and  thence  to  the  tubes. 

There  is  the  usual  provision  of  hand-holes  in  the  water  legs  for 
cleansing  the  tubes,  and  of  doors  in  the  sides  of  the  masonry,  which 
encloses  the  whole  apparatus ;  and  it  will  be  noticed  that  the  drums 
are  at  right  angles  to  the  line  of  the  tubes. 


The  Heine  and  the  Detroit  Water-tube  Boilers 

These  are  two  boilers  very  similar  in  other  respects  to  those  that 
have  been  described,  but  they  have  one  feature  in  common,  in  which 
they  differ  from  the  arrangement  of  other  boilers,  viz.  the  course  of 
the  hot  gases  over  the  tubes.  In  the  Detroit  boiler  there  is  a  brick 
arch  over  the  furnace,  extending  back  under  the  tubes,  for  about  three 
parts  of  their  length.  There  is  the  usual  fire-brick  bridge  at  the  back 
of  the  furnace,  and  the  fire-brick  arch  over  the  furnace  creates  a  com- 
bustion chamber  for  the  hot  gases.  The  hot  gases  pass  along  under 
the  fire-brick  arch,  turn  up  over  the  rear  end  of  the  tubes,  and  along 
the  tubes  longitudinally  to  the  front  end.  They  are  prevented 
from  passing  up  through  the  tubes  to  the  upper  part  of  the  boiler, 
at  the  rear  end,  by  a  tile  baffle  extending  for  about  two-thirds  of  the 
length  of  the  tubes.  The  hot  gases  pass  round  the  end  of  this  baffle 


96      STEAM   BOILERS,   ENGINES,   AND    TURBINES 

and  over  its  top,  under  the  lower  part  of  the  steam  drum,  which  is 
fixed  parallel  with  the  line  of  the  tubes,  and  thence  to  the  chimney 
at  the  rear  end,  the  steam  drum  being  covered  by  brickwork. 


«   Water=tube  Boilers  with  Vertical  Tubes 

Apart  from  the  vertical  boilers  that  will  be  described  later,  and 
that  are  principally  of  a  smaller  type,  used  for  small  work,  there  are 
two  forms  of  water-tube  boilers  in  which  the  tubes  are  arranged  verti- 
cally, or  nearly  so,  they  are  the  Suckling  boilers,  made  by  Messrs. 
E.  K.  and  F.  Turner,  of  Ipswich,  and  the  Sinclair  boiler,  made  by 
Messrs.  George  Sinclair  &  Sons,  Leith.  In  the  Sinclair  there  are  two 
drums,  one  below  for  water  and  the  other  above  for  steam.  In  the 
Suckling  three,  as  shown.  The  upper  drum  corresponds  to  the  steam 
drum  of  other  water-tube  boilers,  and  the  drums  in  both  boilers  stand 
longitudinally  from  front  to  rear  of  the  boiler.  In  the  Sinclair 
boilers  the  upper  and  lower  drums  are  connected  by  vertical  tubes, 
but  in  the  Suckling,  as  will  be  seen,  the  three  drums  are  connected 
by  tubes  slightly  curved  and  nearly  vertical.  In  the  Suckling  boiler, 
which  is  shown  in  section  in  Fig.  15,  the  two  lower  drums  are  slightly 
inclined  from -the  horizontal,  dipping  from  the  front  end  of  the  boiler, 
and  are  fixed  above  the  furnace.  The  drums  are  connected  by  water 
legs,  as  shown,  and  the  vertical  tubes  are  expanded  into  the  drums 
above  and  below  them.  The  rear  portion  of  the  lower  drum  in  the 
Suckling  boiler  is  protected  from  the  furnace  gases  by  a  fire-brick 
arch,  this  arch  forming,  with  the  usual  fire-brick  bridge,  a  combustion 
chamber,  in  which  it  is  claimed  complete  combustion  of  the  hydro- 
carbons, etc.,  is  obtained.  As  will  be  seen  from  the  drawing,  the  hot 
gases  pass  over  the  fire  bridge,  and  thence  vertically  upwards  over 
the  surfaces  of  the  two  lower  drums  and  connecting  tubes.  The  feed- 
water  pipe,  as  will  be  seen  from  the  drawing,  enters  the  upper  drum 
at  the  rear,  and  passes  a  certain  distance  down  the  lower  connecting 
pipe  between  the  two  drums.  There  is  a  small  drum  above  the  boiler 
for  the  steam,  in  addition  to  the  other  three.  It  stands  at  right 
angles. 

In  the  Sinclair  boiler  the  lower  drum  stands  practically  on  the 
ground,  the  furnace  being  fixed  in  the  front  of  it,  and  the  vertical 
tubes  are  fixed  in  the  upper  and  lower  drums,  in  special  landings 
provided  for  them.  Vertical  baffles  are  also  fixed  between  the  tubes, 
dividing  them  into  five  sections,  and  the  hot  gases  pass  from  the  fur- 
nace over  the  fire  bridge,  vertically  upwards  over  the  front  bank  of 
tubes,  between  the  first  baffle  and  the  brick  wall  enclosing  the  boiler, 
over  the  upper  end  of  the  baffle,  down  over  the  next  lot  of  tubes  to 
the  end  of  the  next  baffle,  up  over  the  next  lot,  and  so  on,  passing 


PLATE  GA. — Atlas  Co.'s  Water-tube  Boiler,  with  brickwork  removed. 


PLATE  GB. — Boiler  used  in  the  White  Steam  Cars.     The  water  circulates  through  the 
Tubes,  heat  being  supplied  by  the  Petrol  Burner  shown  below. 

[To  face  p.  96. 


BOILERS 


97 


98      STEAM   BOILERS,   ENGINES,   AND   TURBINES 

from  the  last  bank  of  tubes  through  a  down  take,  in  which  a  super- 
heater is  fixed,  to  the  chimney. 


Water=tube  Boilers  with  Curved  Tubes 

Several  forms  of  water-tube  boilers  have  been  worked  out,  in  which 
the  tubes  are  given  various  curved  forms,  and  are  usually  of  smaller 

size  than  is  common  in 
those  that  have  been  de- 
scribed above. 

The  Climax  Boiler. 
— The  most  striking  form 
of  boiler  with  curved  tubes 
is  the  Climax,  made  in  this 
country  by  Messrs.  B.  E. 
Eowland  &  Co.  It  is 
shown  in  Fig.  16.  The 
principal  feature  of  the 
boiler  is  the  small  floor 
space  it  occupies,  the  ap- 
paratus being  arranged 
vertically  instead  of  hori- 
zontally. The  arrange- 
ment of  the  water  tubes 
also  is  peculiar  to  itself 
and,  so  far  as  the  author 
is  aware,  is  not  like  any 
other  boiler.  Further, 
the  whole  arrangement  is 
unique.  There  is  the 
usual  steam  drum,  con- 
taining water  and  steam, 
as  generated,  but  it  is 
fixed  vertically  in  the 
centre  of  the  boiler.  The 
water  tubes  look  very 
much  like  a  coil  of  rope, 
or  one  of  the  coils  of 
taper  that  used  to  be  used 
for  sealing-wax  in  days 
FIG.  16. — Internal  View  of  Climax  Water-tube  Boiler,  gone  by  There  are  a  very 
showing  the  Tubes,  Vertical  Steam  Drum,  etc.  large  number  Of  tubes, 

and   they  are   bent   into 

the  form  of  a  loop,  of  a  somewhat  irregular  shape,  the  form  being 
necessary,  as  will  be  seen  from  Fig.  16,  because  each  tube  has  to  be 


•  BOILERS  99 

threaded  in  with  the  others.  Each  tube  commences  and  ends  in  the 
central  drum,  but  one  end  of  each  is  always  at  a  higher  level  than  the 
other,  and  it  will  be  understood  that  the  water  in  the  tubes  is  con- 
tinually passing  from  each  tube  into  the  central  drum,  out  into  another 
tube,  back  to  the  drum,  and  so  on.  The  upper  portion  of  the  central 
cylinder  has  also  a  series  of  diaphragms,  which  it  is  claimed  form  a 
series  of  superheating  chambers,  through  which  the  steam  is  compelled 
to  pass  in  its  passage  through  successive  loops  of  the  tubes.  The 
tubes  are  surrounded  on  the  outside  by  a  thermal  insulating  wall,  and 
outside  of  that  again  is  an  iron  casing  enclosing  the  whole  apparatus, 
the  upper  part  of  which  is  coned,  its  centre  joining  the  chimney. 
The  central  cylinder  descends  right  to  the  bottom  of  the  structure, 
the  bottom  providing  a  space  to  which  any  sediment  in  the  water 
can  fall,  and  this  portion  of  the  cylinder  being  accessible  by  means 
of  a  manhole  door.  The  water  tubes  are  supported  simply  by  their 
connection  with  the  central  steam  drum,  which  is  made  of  the  usual 
steel  of  high  tensile  strength,  welded  longitudinally,  in  place  of 
being  riveted.  Space  is  left  below  the  lowest  tube,  sufficient  for 
four  furnaces,  as  shown  in  the  figure,  which  are  of  the  usual  con- 
struction, with  fire  bridge,  etc.,  at  the  back,  and  the  hot  gases  from 
the  furnace  pass  straight  up  between  the  interstices  of  the  tubes,  and 
over  the  surface  of  the  central  cylinder.  The  upper  portion  of  the 
central  cylinder  is  made  dome-shaped,  and  forms  the  steam  space, 
the  steam  pipe  being  connected  to  it.  The  conical  space  above  the 
tubes  is  also  made  use  of  for  the  purpose  of  holding  a  feed-water 
heater,  of  somewhat  novel  construction. 

The  feed-water  heater  consists  of  a  coil  of  pipe  100  to  300  feet  in 
length,  according  to  the  size  of  the  boiler,  the  pipe  being  from  1J 
inch  to  3  inches  in  diameter,  and  welded.  This  coil  of  pipe  is  fixed 
inside  the  conical  space,  above  the  water  tubes.  It  surrounds  the 
upper  part  of  the  central  cylinder,  and  is  therefore  exposed  to  the 
heat  of  the  hot  gases  as  they  pass  to  the  chimney  above.  The  feed 
water  is  passed  into  this  coil  of  tube,  and  from  thence  to  the  lower 
part  of  the  central  cylinder,  from  which  it  passes  to  the  lower  tubes, 
thence  circulating  through  successive  layers  of  the  tubes,  becoming 
.hotter  as  it  passes  upwards,  steam  being  formed  and  disengaged  in 
the  central  cylinder  as  the  water  passes  into  it  from  each  tube  in 
succession. 


The  Thornycroft  Water-tube  Boilers 

Messrs.  Thornycroft's  boilers  have  been  designed  principally  for 
torpedo-boats,  steam-launches,  and  similar  work,  but  they  are  also 
used  on  shore.  The  principal  feature  in  connection  with  them,  is 


ioo    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  small  size  of  the  tubes,  and  the  special  arrangements  that  have 
been  made  for  securing  a  large  heating  surface,  and  the  passage  of  the 
hot  gases  over  the  whole  length  of  the  tubes.  There  are  two  principal 
forms  made  by  the  firm,  known  respectively  as  the  Thornycroft- 
Marshall,  and  the  Thornycroft-Schultz.  In  the  Thornycroft-Marshall 
boiler,  there  are  a  number  of  tubes  slightly  curved,  fixed  to  a  header  at 
the  back,  something  on  the  lines  of  the  central  cylinder  in  the  Climax, 
successive  lengths  of  tube  being  connected  together  by  connecting 
pieces  at  the  front,  two  lengths  forming  together  a  loop,  somewhat 
similar,  though  different  in  form,  to  the  loop  of  the  Climax  boiler, 
and  with  a  steam  drum  at  the  top  in  front,  the  drum  being  fixed  at 
right  angles  to  the  line  of  the  boiler.  The  tubes  are  staggered,  and 
the  furnace  is  below  the  lowest  tube,  the  hot  gases  passing  up  simply 
through  the  interstices  of  the  tubes  to  the  chimney  at  the  top,  the 
water  circulating  in  the  tubes  very  much  as  in  the  Climax,  steam 
being  disengaged  in  the  back  header,  and  rising  to  the  steam  drum. 
This  boiler  is  made  also  with  straight  tubes,  arranged  in  a  similar 
manner,  in  loops,  as  the  curved  tubes.  It  is  also  made  in  what  is 
termed  the  sectional  form.  The  tubes  in  the  sectional  form  are 
all  straight,  one  set  of  tubes  of  a  section  being  inclined  to  the  hori- 
zontal in  one  direction,  and  the  other  set  of  the  same  section  being 
inclined  to  the  horizontal  in  the  opposite  direction.  Each  set  of 
tubes  of  a  section  are  expanded  into  a  front  header,  one  below  the 
other.  The  two  sets  of  tubes  are  connected  together  by  junction 
pieces  at  the  back,  in  a  similar  manner  to  the  tubes  of  the  other 
boilers  of  this  type.  The  furnace  is  below  the  lowest  tubes,  as  before, 
the  hot  gases  passing  up  between  the  tubes,  and  the  steam  drum 
being  fixed  in  front  of  the  boiler,  at  right  angles  to  the  line  of  the 
tubes,  and  connected  to  the  header  of  the  tubes  which  rise  towards  it. 


Thornycroft-Schultz  Boiler 

The  Thornycroft-Schultz  boiler,  one  form  of  which  is  shown  in 
Plate  4B,  was  introduced  by  Mr.  Thornycroft  specially  for  marine 
work,  and  in  particular  for  small  craft,  such  as  torpedo-boats,  and 
torpedo-boat  destroyers,  where  it  is  important  to  have  the  ability  to 
raise  a  comparatively  large  quantity  of  steam  in  a  small  space,  and 
to  be  able  to  raise  steam  very  quickly.  It  is  made  in  several 
forms,  according  to  the  vessel  in  which  it  is  to  be  employed.  The 
earliest  form,  shown  in  Fig.  17,  was  known  as  the  "  Speedy  "  type, 
and  has  three  drums  running  fore  and  aft,  two  placed  below,  as  will 
be  seen,  and  the  third  above.  The  lower  drums  are  for  water,  and 
the  upper  one  is  the  steam  drum.  The  upper  drum  is  connected 
with  the  lower  drums  by  a  bank  of  small  tubes,  1  to  H  inch  in 


BOILERS  101 

diameter,  curved  as  shown.  In  the  later  forms  of  this  boiler  the  tubes 
are  only  slightly  curved,  sufficiently  to  allow  space  between  them,  and 
make  a  nearly  direct  connection  between  the  two  drums,  a  large  portion 
of  the  tubes  entering  the  water  space  in  the  steam  drum,  and  only  a 
small  portion  entering  it  in  the  steam  space.  The  steam  drum  is  also 
connected  to  each  of  the  water  drums  by  the  two  large  pipes  shown. 
The  small  tubes  are  for  the  generation  of  steam,  and  the  large  tubes  are 
for  water  circulation,  to  return  any  water  carried  into  the  steam 
drum  back  to  the  water  drums,  and  also  to  convey  the  feed  water, 
which  is  delivered  into  the  lower  part  of  the  steam  drum,  to  the 
water  drums.  The  generating  tubes  are  enclosed  in  a  steel  casing,  as 
shown,  lined  with  asbestos.  This  means  that  the  whole  of  the 
boiler,  except  the  front,  where  the  large  tubes  are  placed,  is  enclosed 


FIG.   17. — Longitudinal   and  Transverse   Sections   of  the   Thornycroft  Water-tube 

Boiler,  "Speedy"  type. 

within  the  casing.  A  small  portion  of  the  generating  tubes  also  are 
formed  into  a  sort  of  water-tube  wall,  the  tubes  being  placed  very 
close  together,  near  the  casing,  and  so  enclosing  the  hot  gases.  The 
chimney  rises  from  the  middle  of  the  casing,  and  the  furnace  is 
placed  in  the  middle  of  the  space  at  the  bottom  between  the  water 
drums,  the  hot  gases,  rising  from  the  furnace,  pass  between  the 
interstices  in  the  tubes,  round  the  steam  drum,  and  thence  to  the 
chimney. 

In  the  second  form  of  this  type  of  boiler,  known  as  the  "  Daring  " 
type,  from  the  torpedo-boat  destroyer  in  which  it  was  first  intro- 
duced, there  are  two  drums,  also  standing  fore  arid  aft,  but  placed 
vertically  one  above  the  other,  the  upper  one,  which  is  much  larger 
than  the  lower,  is  the  usual  steam  drum,  in  which  steam  and  water 
are  present,  and  the  lower  drum  is  for  water  only.  The  boiler  is  shown 


102    STEAM  BOILERS,  ENGINES,   AND   TURBINES 

in  Fig.  18.  The  two  drums  are  connected  by  eight  or  nine  large 
tubes,  of  about  4  inches  in  diameter,  arranged  practically  in  a  vertical 
line  between  the  two,  and  also  by  two  sets  of  smaller  generating 
tubes,  curved  in  the  forms  shown,  a  portion  of  the  generating  tubes 
being  placed  close  together,  and  forming  a  water-tube  wall,  as  in  the 
"  Speedy  "  type.  The  whole  is  enclosed  in  a  steel  case  as  before,  and 
there  are  two  sets  of  furnaces,  one  on  each  side  of  the  water  drum, 
and  the  chimney  rises  from  the  rear  of  the  boiler.  The  hot  gases 
rise  from  the  furnace,  play  over  and  through  the  generating  tubes, 
and  under  and  around 't  the  steam  drum,  and  pass  out  by  the 
chimney. 

The  launch  type  of  boiler  is  described  by  Messrs.  Thornycroft,  as 
half  a  "  Daring  "  type.  There  are  the  same  two  drums,  the  steam 
drum  above,  and  the  water  drum  below,  connected  by  the  large 


FIG.    18. — Transverse  and  Longitudinal   Sections  of  the  Thornycroft  Water-tubo 

Boiler,  "Daring"  type. 

tubes,  and  by  the  two  curved  sets  of  small  tubes,  with  the  space 
between  the  two  curved  sets  for  the  furnace,  and  for  the  hot  gases 
to  play.  The  whole  is  enclosed  as  before  in  a  steel  case,  the  chimney 
rising  from  the  middle. 

In  the  Schultz  form  of  boiler  proper  there  are  four  drums,  one 
large  steam  drum  above,  and  three  water  drums  below,  one  im- 
mediately under  the  steam  drum,  and  one  on  each  side,  and  the 
steam  drum  is  connected  to  the  three  water  drums  by  curved  tubes, 
a  water-tube  wall  being  formed  on  the  outside  of  the  outer  bank 
of  tubes,  as  in  the  others,  and  two  furnaces  being  fixed  between  the 
centre  water  drum  and  the  drum  on  each  side  of  it.  The  whole  is 
encased  in  a  steel  case,  the  chimney  rising  from  the  centre,  as  before, 
and  the  hot  gases  passing  up  from  the  furnaces  playing  round  the 
generator  and  other  tubes,  and  passing  out  to  the  chimney. 


BOILERS 


104-    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Taylor  Water=tube  Boiler 

This  boiler,  which  is  American,  is  made  for  marine  engines,  and, 
it  is  claimed,  exposes  a  very  large  heating  surface  to  the  hot  gases. 
The  water  tubes  are  of  1£  inch  in  diameter,  and  they  are  built  into 
a  rectangular  form.  They  are  formed  into  rectangular  boxes 
by  short  lengths  of  vertical  tubes,  ending  in  horizontal  headers, 
formed  of  pipes  of  larger  section.  The  furnaces  are  underneath  the 
lower  bank  of  tubes,  and  the  hot  gases  rise  through  the  rectangular 
spaces,  and  play  all  round  the  walls  of  the  tubes.  Above  the  topmost 
box  of  tubes  is  the  usual  steam  drum,  and  the  whole  is  enclosed 
inside  steel  casing,  the  chimney  rising  from  the  centre. 

Fig.  19  shows  a  transverse  and  longitudinal  section  of  the  Hay 
water-tube  boiler  that  has  recently  been  introduced,  and  is  intended 
principally  for  marine  work.  Its  principal  feature  is  the  curve  given 
to  the  tubes,  as  seen  in  the  figure,  some  of  the  tubes  being  used  for 
steam,  others  for  water. 


Small  Vertical  Boilers 

There  is  a  class  of  boilers  made  for  small  work,  consisting  usually 
of  a  vertical  cylinder,  made  from  open-hearth  steel,  in  the  same 
manner  as  the  Lancashire  boiler.  They  are  used  for  portable  and 
semi-portable  engines,  the  engines  being  mounted  on  a  bed  plate,  or 
on  a  wheel  base  by  the  side  of  the  boiler,  and  are  also  used  for 
those  many  cases  where  steam  is  employed  for  small  industries, 
and  in  which  very  low  pressure,  5  Ibs.,  etc.,  are  employed.  They 
are  made  on  both  the  water-tube  and  fire-tube  plan.  In  both  forms 
there  are  tubes  fixed,  sometimes  horizontally  across  the  boiler, 
sometimes  vertically  between  the  water  and  steam  spaces.  The 
furnace  occupies  the  lower  part  of  the  cylinder,  the  grate  bars  being 
fixed  sufficiently  above  the  ground  to  allow  for  an  ashpit  underneath, 
and  the  chimney  sometimes  rises  from  the  centre  of  the  cylinder, 
and  sometimes  from  the  side.  In  either  case  the  hot  gases  pass 
around  the  tubes,  when  they  are  water  tubes,  and  through  them 
when  they  are  fire  tubes,  and  find  their  way  to  the  chimney. 

Boilers  for  motor-cars,  motor-waggons,  etc.,  steam-driven  waggons, 
lorries,  etc.,  have  special  forms.  They  are  sometimes  fired  with 
coal,  preferably  anthracite,  but  more  frequently  with  either  petrol, 
paraffin,  or  one  of  the  oils  obtained  from  the  distillation  of  petroleum. 

The  Thornycroft  Steam  Waggon  Company,  and  Messrs.  Straker, 
have  both  worked  out  forms  of  boilers  for  use  with  anthracite  or 


BOILERS 


105 


coke.  The  Straker  boiler,  which  is  shown  in  Fig.  20,  is  a  water- 
tube  boiler,  constructed  something  on  the  lines  of  the  Climax,  but 
without  the  curved  tubes  that  are  such  an  important  feature  in  that 
boiler.  There  are  four  concentric  tubes  fixed  vertically,  and  between 
two  of  them,  as  shown,  are  fixed  cross  tubes  radially,  and  slightly 


FIG.  20. — Sectional  Elevation  of  the  Straker  Boiler  for  Steam-driven  Vehicles.    The 
water  is  in  the  tubes,  and  the  hot  gases  pass  up  between  them. 

inclined  from  the  centre  outwards,  The  bottom  portion  of  the 
apparatus  forms  the  fire-box,  with  an  ashpit  below,  and  it  is  fed 
from  above,  by  way  of  the  central  tube ;  the  radial  tubes  are  placed 
in  echelon,  the  effect  being  the  same  as  the  staggering  of  the  tubes 
in  ordinary  water-tube  boilers,  and  the  hot  gases  pass  up  through 
the  spaces  between  the  tubes,  and  thence  find  their  way  to  the 
chimney. 

The  Thornycroft  boiler  is  also  of  the  water-tube  type.    It  consists 


io6    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

of  two  annular  chambers,  fixed  horizontally  one  above  the  other,  the 
two  being  connected  by  a  number  of  small  straight  steel  tubes.  The 
furnace  is  below,  as  in  the  Straker,  and  the  hot  gases  pass  from  it 
round  the  tubes,  and  the  underside  of  the  upper  annular  ring,  and 
find  their  way  to  the  chimney.  Of  the  oil-fired  boilers  for  motor- 
cars, waggons,  etc.,  the  White,  an  American  apparatus,  is  perhaps 
the  best  known.  The  arrangement  of  the  boiler  is  shown  in  Plate  GB. 
The  boiler,  it  will  be  seen,  consists  of  a  coil  of  tubes,  the  burner 
being  of  the  ring  form,  with  a  special  arrangement  for  carburizing 
the  oil  as  it  comes  from  the  burners.  The  action  of  the  burner  is 
very  similar  to  that  of  the  ordinary  gas-ring  burner,  so  well  known, 
with  the  addition  of  a  provision  for  warming  the  oil  on  its  way  to 
the  burner,  for  the  purpose  of  vapourizing  it.  The  water  for  the 
boiler  is  fed  into  the  upper  end  of  the  coil,  passing  downwards  from 
section  to  section,  and  before  it  has  reached  the  point  at  which  it  is 
taken  off  to  the  engine,  it  has  become  steam,  and  has  been  thoroughly 
dried  and  superheated,  this  being  one  of  the  special  features  which 
enables  the  boiler  to  be  worked  successfully. 

In  the  Turner-Miesse,  which  is  made  in  England,  the  boiler,  or 
generator,  as  the  makers  of  motor-cars  prefer  to  call  it,  consists  of 
layers  of  zigzag  coils  of  pipe,  fixed  at  right  angles  to  each  other, 
inside  a  casing,  and  with  a  burner  underneath.  The  water  in  this 
case  enters  the  boiler  in  the  lower  layers,  but  after  being  converted 
into  steam,  is  brought  down  again  to  some  of  the  intermediate  layers, 
those  at  right  angles  to  the  water  layers,  where  it  is  dried  and  super- 
heated before  being  passed  to  the  engine. 


CHAPTER  III 

BOILER  ACCESSORIES 

Burning  the  Fuel 

The  Furnace  Grates. — Except  in  the  case  of  some  special  boilers 
where  liquid  fuel  is  burned,  and  of  some  others  that  will  be 
described,  the  grates  of  all  boilers  are  very  much  alike.  They  are 
merely  horizontal  platforms,  built  of  sectional  pieces  of  iron,  arranged 
to  hold  the  fuel  in  such  a  manner  that  air  can  pass  up  from  the 
ashpit  into  the  fuel,  and  the  ashes  can  pass  down  into  the  ashpit. 
The  usual  length  of  the  fire  grate  from  back  to  front  is  6  feet,  and 
it  is  generally  formed  of  two  sets  of  fire  bars  made  of  cast-iron, 
supported  in  front  by  bars  resting  on  the  dead  plate,  and  at  the 
back  by  other  bars  resting  on  the  bridge,  the  supporting  bars  having 
slots  into  which  the  ends  of  the  fire  bars  fit.  At  the  middle  of 
the  furnace  the  fuel  bars  are  supported  in  a  similar  manner  by  a 
bearing  bar. 

In  nearly  all  furnaces  there  is  the  fire-brick  bridge  at  the  back, 
that  has  been  referred  to  so  often  in  the  course  of  the  previous 
chapter,  the  office  of  which  is  to  enable  the  fire  to  be  built  of  a 
certain  thickness,  to  form  a  sort  of  holder  for  the  front  portion  of 
the  fire,  and  by  itself  becoming  white  hot,  to  assist  in  the  combustion 
of  the  hydrocarbon  gases,  the  finely  divided  carbon,  etc.,  that  so  often 
comes  away  from  the  fuel  unburned. 

In  the  Lancashire  and  Cornish  boilers,  the  marine  boiler,  and  in 
those  multitubular  boilers  which  are  internally  fired,  the  fire  grates 
occupy  the  front  portions  of  the  flues.  In  the  water-tube  boilers  the 
fire  grates  occupy  the  front  of  the  large  rectangular  space  enclosed 
by  the  brickwork,  as  described.  In  the  Lancashire  and  Cornish  and 
other  internally  fired  fire-tube  boilers,  the  lower  portion  of  the  flues, 
in  which  the  fire  grates  are  fixed,  form  the  ashpits,  and  it  is  through 
these  that  air  enters  the  boiler,  and  through  them  that  the  ashes, 
clinker,  etc.,  are  drawn  out. 

In  the  water- tube  boilers  the  ashpit  is  practically  on  the  ground, 


io8    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

protected  from  fire,  etc.,  and  the  back  portion  of  the  rectangular 
space  enclosed  by  the  brick  and  steel  structure  is  often  employed  as 
a  combustion  chamber,  and  it  is  sometimes  arranged  that  the  ashes 
fall  over  the  back  of  the  furnace,  into  the  space  below,  or  into  a 
chamber  provided  for  them. 

The  fronts  of  all  furnaces  are  closed  by  one  or  two  fire  doors,  the 
ashpits  being  sometimes  closed  and  sometimes  not.  As  will  be 
explained,  with  what  are  termed  natural  and  induced  draught,  the 
ashpit  is  left  open  for  the  air  to  pass  in  under  the  fire  bars,  and 
thence  through  the  fuel.  With  one  form  of  forced  draught  the  ash- 
pit is  closed,  and  the  air  is  forced  into  it  through  a  pipe  provided  for 
the  purpose. 

The  furnace  doors  are  sometimes  single  and  sometimes  double. 
They  sometimes  swing  on  hinges,  and  sometimes  slide  along  the  face 
of  the  boiler,  in  a  similar  manner  to  bulkheads  on  board  ship,  the 
two  doors  opening  and  closing  together,  and  being  kept  in  position 
by  balance  weights. 


/  Special  Forms  of  Furnace  Bars 

Several  special  arrangements  of  furnace  grates  have  been  intro- 
duced, with  the  object  of  cleaning  the  fires  quickly,  without  opening 
the  furnace  doors,  and  to  maintain  a  more  constant  draught  than  is 
sometimes  possible  with  the  ordinary  bar. 

It  will  be  understood  that  with  the  ordinary  bar,  built  into  a 
grate,  with  practically  all  kinds  of  fuel,  the  spaces  between  the  bars 
are  gradually  filled  up  by  the  incombustible  clinker  that  is  formed 
from  the  coal,  and  this  results,  first  in  a  reduction  of  the  draught,  or, 
to  put  it  more  correctly,  in  an  increase  of  the  resistance  to  the  passage 
of  the  air  into  the  fuel,  and  later  on,  to  the  necessity  for  cleaning  out 
the  fires  in  order  to  get  rid  of  the  clinker ;  as,  if  the  clinkering  is 
allowed  to  go  on,  the  apertures  between  the  bars  will  be  completely 
stopped  up.  It  is  to  avoid  this  that  the  moving  bars  in  all  forms  of 
mechanical  stokers  are  employed,  the  clinker,  as  described  later  on, 
being  automatically  carried  to  the  back  of  the  furnace.  The  special 
forms  of  furnace  bars  to  be  described  aim  at  accomplishing  the  same 
object,  without  the  automatic  feeding  which  constitutes  the  special 
feature  of  mechanical  stokers.  In  Fig.  21  Neil's  rocking  fire  bars 
are  shown  in  a  complete  grate  6  feet  long  by  3  feet  wide,  built  up 
of  two  sets  of  fire  bars,  longitudinally,  each  set  comprising  five  bars 
fixed  side  by  side.  The  modus  operandi  is  as  follows.  The  fuel  is 
fed  on  to  the  fire  bars  in  the  usual  way,  and  is  allowed  to  burn  for 
a  certain  time,  and  when  the  boiler-attendant  considers  it  necessary — 
this  point  is,  of  course,  determined  by  experience — the  handle  shown 


BOILER  ACCESSORIES 


109 


on  the  left  is  moved,  and  the  whole  of  the  bars  rock  quickly  on  their 
axes,  allowing  the  clinker  to  fall 
into  the  ashpit  below.  Mr.  Neil 
also  makes  a  fire  grate  with  a 
special  furnace  door,  as  shown  in 
Fig.  22,  leaving  a  baffle  plate  be- 
tween the  furnace  front  proper  and 
the  front  of  the  grate,  the  dead 
plate  being  in  front  of  the  baffle 
plate.  The  object  of  the  baffle  plate 
is  to  protect  the  furnace  door,  and 
its  brackets,  from  the  flames  of  the 
furnace,  and  also  to  heat  auxiliary 
air  that  may  be  allowed  to  pass  over 
the  fuel  for  the  purpose  of  quench- 
ing smoke.  It  will  be  seen  that 
any  air  which  passes  through  the 
furnace  door  has  to  pass  through 
the  holes  in  the  hot  baffle  plate 
before  reaching  the  furnace.  It 
will  be  noticed  that  there  are  air 
spaces  in  the  fire  bars,  the  adjacent 
bars  being  fitted  very  closely  to- 
gether. 

In  another  form  of  rocking  fire 
grate,  made  by  the  E.  Keeler  Com- 
pany of  Williams  Port,  Pennsylvania, 
the  fire  bars  are  arranged  in  rows,  at 

right  angles  to  the  line  of  the  fur-  _    "T,  .,,    XT  -v 

-£,,-1         .     .      , ,       «  FIG.  21. — Furnace   Grate  with   Neil  s 

nace.     Each  fire  bar  is  in  the  form  Hocking  Fire  Bars. 

of  a  crescent,  fitting  on  the  spindle 

common  to  its  row,  and  the  whole  of  them  are  rocked  from  front  to 


FIG.  22. — Neil's  Furnace  Front,  with  Baffle  Plate  between  the  Furnace  and  Fire  Door, 
back,  so  that  the  clinker  is  automatically  thrown  downwards  by  the 


i  io    STEAM  BOILERS,   ENGINES,  AND   TURBINES 


action.  The  Keeler  Com- 
pany also  make  a  grate  bar, 
built  up  of  a  number  of 
V-shaped  bars,  held  between 
two  parallel  sides,  the  whole 
being  cast  in  one,  the  spaces 
between  the  V's  allowing 
air  to  pass  up  into  the 
fuel. 

There  is  another  form  of 
rocking  fire  bar,  made  by 
Messrs.  Neemes  Bros.,  of 
Troy,  New  York,  that  is  very 
similar  to  the  Keeler,  but 
with  a  space  between  the 
bars. 


Apparatus  for  Burn- 
ing Coal  Dust 

Coal  dust  may  be  burnt 
in  Messrs.  Meldr urn's  fur- 
nace, described  on  p.  114,  or 
it  may  be  burnt  by  special 
apparatus,  such  as  that 
worked  out  by  Mr.  Schwartz- 
kopff  and  that  known  as  the 
Cyclone  apparatus.  With 
either  of  these  apparatus  the 
coal  is  first  reduced  to  a  very 
fine  powder  by  the  aid  of 
machinery  designed  for  the 
purpose,  and  is  then  delivered 
to  the  furnace  in  the  form  of 
a  fine  spray,  similar  to  the 
spray  formed  from  petrol  in 
motor  engines.  The  object 
to  be  attained,  in  both  cases, 
is  the  division  of  the  sub- 
stance into  very  fine  par- 
ticles and  the  spreading  of 
the  particles  into  the  air 
that  is  supplied  to  the  fur- 
nace, so  that  each  particle 


BOILER   ACCESSORIES 


ii  i 


of  dust  can  seize  upon  the  oxygen  it  requires  to  complete  its 
combustion. 

In  the  Schwartzkopff  apparatus,  which  is  shown  in  section  in 
Fig.  23,  the  coal  dust  is  taken  to  a  hopper  above  the  entrance  to 
the  furnace,  and  is  led  down  into  the  furnace  by  a  revolving  brush, 
as  shown,  which  spreads  the  dust  out,  and  delivers  it  in  a  fine  cloud 
into  the  furnace,  very  much  as  petrol  and  air  are  delivered  to  the 
cylinder  of  a  motor-car  engine.  Induced  draught  is  employed  with 
the  apparatus,  and  the  combined  operation  of  the  brush  and  the 
sucking  action  of  the  induced  draught  provides  a  continual  supply 
of  air  and  fuel  to  the  furnace. 

In  the  Cyclone  apparatus  the  coal  dust  is  taken  to  a  hopper,  as 
with  the  Schwartzkopff,  but  it  is  delivered  to  the  furnace  solely 
by  the  aid  of  the  fan  that  is  employed  to  furnish  the  draught,  forced 
draught  being  used. 


Apparatus  for  Burning  Liquid  Fuel 

The   Holden   System. — In    the  Holden    apparatus,   which  is 
arranged  for  burning  liquid  fuel,  either  separately  or  in  conjunction 


FIG.  24. — Sectional  Drawings  of  Holden's  Apparatus  for  Burning  Liquid  Fuel,  as 
applied  to  a  Lancashire  Boiler. 

with  solid  fuel  of  an  inferior  quality,  and  for  burning  the  fuel  in 
the  strictly  liquid  form,  or  in  the  form  of  the  pasty  mass  known 
as  refuse,  a  steam  injector  is  employed.  The  apparatus  is  applicable 
to  all  kinds  of  boilers,  though  it  was  worked  out  originally  for  use 
with  the  boilers  of  locomotive  engines.  The  liquid  fuel  is  held  in 
any  convenient  receptacle  near,  and  is  led  to  the  fire-box  by  a  pipe, 
as  shown  in  Fig.  24,  and  is  forced  into  the  fire-box,  or  combustion 


ii2     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


chamber,  in  the  form 
of  a  fine  spray,  by  the 
aid  of  a  steam  injector. 
The  injector  forces  the 
fuel  into  the  fire-box 
in  the  same  manner 
as  water  is  forced  into 
the  boiler. 

Where  a  low-grade 
fuel  is  employed  in 
addition  to  liquid  fuel, 
a  thin  layer  of  the  fuel 
is  laid  on  the  fire  bars, 
and  the  jet  of  liquid 
fuel  is  directed  on  to  it. 

In  this  apparatus, 
as  in  other  forms  of 
liquid  fuel  burning 
apparatus,  the  furnace 
forms  a  combustion 
chamber,  the  fire  bars 
merely  being  employed 
to  supply  the  neces- 
sary air  to  combine 
with  the  carbon  and 
hydrogen  of  the  fuel. 

The  apparatus  is 
applied  to  Lancashire 
and  other  boilers,  by 
merely  cutting  a  hole 
in  the  door  of  the 
furnace,  and  inserting 
the  pipe  and  injector 
nozzle.  Proper  cocks 
regulate  the  supply  of 
fuel  and  steam.  Steam 
for  the  injector  is  taken 
from  the  boiler. 

Liquid  Fuel 
Burners 

Marshall's  Ap- 
paratus.—  Messrs. 
Marshall  &  Sons,  of 


PLATE  7 A. — Outside  View  of  Medrum's  Furnaces  for  Low-grade  Fuels,  as  fitted  at 
a  Colliery.  The  Boilers  are  at  the  back,  their  Flues  being  connected  to  the 
Furnaces. 


I 


PLATE  TB.— A  Pair  of  Water  Tube  Boilers,  with  Chain  Grate  Stokers. 

[To  face  p.  112. 


BOILER  ACCESSORIES  113 

Gainsborough,  have  also  worked  out  an  apparatus  for  burning  liquid 
fuel  that  can  be  applied  to  boilers  of  any  type.  The  fuel  is  carried  in 
a  galvanized  iron  tank,  standing  near  the  boiler  in  which  it  is  to  be 
consumed,  and  the  tank  is  warmed  by  a  copper  coil,  through  which 
steam  passes  from  the  boiler,  the  condensed  steam  being  carried  off  in 
the  usual  way.  Warming  the  fuel  renders  it  more  easily  handled, 
and  enables  the  pasty  substances  mentioned  to  be  handled  as  liquids. 


FIG.  26— Korting's  Liquid  Fuel 
Burning  Apparatus,  applied 
to  a  Locomotive. 


FIG.  27. — Shows  its  application  to  a  Lanca- 
shire Boiler. 


The  fuel  is  driven  into  the  furnace,  under  the  fire  bars,  in  a  manner 
very  similar  to  that  described  with  the  Holden  apparatus,  by  means 
of  an  injector.  As  shown  in  Fig.  25,  a  pipe  from  the  fuel  tank  leads 
to  the  ashpit  of  the  boiler,  and  a  steam  pipe  from  the  boiler  leads 
there  also,  the  injector  driving  in  the  fuel  into  the  furnace  in  a  fine 
spray,  as  already  described.  Figs.  26  and  27  show  Korting's  liquid 
fuel  burning  apparatus. 


Burning  Town's  Refuse 

Town's  refuse  has  a  small  calorific  value,  since  a  large  portion  of 
the  material  of  which  it  is  composed  contains  a  certain  quantity  of 
carbon,  though  there  is  also  a  very  large  proportion  of  incombustible 
material.  Its  average  evaporative  value  is  about  1  Ib.  of  refuse  to 
1  Ib.  of  water  evaporated  from,  and  at  212°  F.  the  average  evapo- 
rative duty  of  coal  being  8  Ibs.  Kefuse,  it  will  be  easily  understood, 

I 


ii4    STEAM  BOILERS,   ENGINES,  AND  TURBINES 

varies  very  considerably,  some  of  it  in  certain  districts  having  a 
value  only  half  the  average,  and  some  in  other  districts  having  a 
value  of  twice  the  average. 

There  are  several  refuse  destructors  on  the  market,  all  on  certain 
lines,  with  the  usual  variations.  In  all  of  them  there  is  a  furnace — 
a  modification  of  the  ordinary  boiler  furnace — with  usually  some 
arrangement  for  drying  the  green  refuse,  the  freshly  deposited  refuse, 
before  it  is  pushed  on  to  the  furnace  bars  proper.  There  is  also  in 
all  forms  of  the  apparatus  either  a  chamber  or  a  special  flue,  whose 
walls  are  maintained  at  a  very  high  temperature,  so  that  the  green 
gases,  as  they  are  called,  the  gases  which  are  produced  by  the  first 
combustion  of  the  refuse,  are  submitted  to  a  temperature  of  1500°  to 
2000°  F.  in  this  chamber  or  flue.  The  reason  for  this  is,  unless 
this  is  done,  the  smoke  and  gases  that  are  emitted  from  the  chimney 
may  be  a  nuisance  to  the  neighbourhood,  as  they  contain  substances 
that  will  form,  with  the  bacilli  in  the  neighbourhood,  noxious  pro- 
ducts that  give  rise  to  disease,  etc.  In  addition,  in  all  forms  of  the 
apparatus,  there  is  some  arrangement  for  creating  forced  draught, 
and  usually  for  warming  the  air  before  it  enters  the  furnace,  a  steam 
jet  being  a  favourite  form  of  draught-producing  apparatus,  and  the 
hot  gases,  after  passing  through  the  high-temperature  chamber 
mentioned  being  caused  to  warm  the  air  passing  to  the  furnace  by 
a  system  of  pipes  similar  to  those  described  on  p.  162  in  connection 
with  Green's  apparatus.  In  all  of  them  also  some  appliance  is 
necessary  for  depositing  the  large  quantities  of  dust  that  are  formed 
in  the  process  of  combustion,  and  preventing  them  passing  out  to  the 
atmosphere  outside.  In  the  Horsfall  apparatus  there  is  a  whirling 
chamber  at  the  base  of  the  chimney,  in  which  the  dust  is  carried  into 
side-depositing  chambers  by  centrifugal  force.  In  Meldr urn's  and 
other  apparatus  there  are  settling  chambers  of  different  forms.  The 
hot  gases,  after  passing  through  the  combustion-chambers  mentioned, 
are  led  to  boiler  flues  in  the  usual  manner,  the  refuse-destructor 
combustion  chamber  being  directly  connected  to  the  boiler  flues  or 
the  space  for  the  gases  in  the  water- tube  boiler. 


Meldrum's  Colliery  Refuse  Destructor 

Messrs.  Meldrum,  who  have  fitted  up  a  number  of  refuse  destruc- 
tors for  town's  refuse,  have  also  worked  out  a  modification  of  their 
refuse  destructor  for  burning  the  inferior  fuel  that  is  so  often  found 
in  collieries  on  the  margin  of  the  coal  seams  and  sometimes  between 
them.  The  substances  mentioned  are  unsaleable  on  the  market,  as 
their  calorific  value  is  so  low,  but  when  applied  in  the  manner 
described,  they  answer  very  well  for  raising  steam. 


BOILER  ACCESSORIES  115 

In  Messrs.  Meldrum's  apparatus,  an  external  view  of  one  of 
which  is  shown  in  Plate  7  A,  the  principal  feature  is  the  grate,  in  which 
the  bars  are  made  very  thin,  and  placed  very  close  together,  as  shown 
in  Fig.  28,  and  the  draught  is  produced  by  Messrs.  Meldrum's 
method  of  steam  injection,  as  explained  on  p.  147. 


O 


0 


FIG.  28. — Section  and  Plan  of  Meldrum's  Interlocking  Fire  Bars,  for  burning  refuse 
fuel.     The  bars  are  thin  and  very  close  together. 

At  the  back  of  the  furnace  is  a  combustion  chamber,  very  much 
on  the  lines  of  that  employed  in  town's  refuse  destructors,  in  which 
the  hydrocarbons  and  all  combustible  matter  coming  over  from  the 
furnace  are  burned,  and  this  is  directly  connected  with  the  boiler  flues 
or  the  gas  space  of  the  water-tube  boiler  by  a  special  flue  connection. 
The  whole  arrangement  is  shown  very  clearly  in  Fig.  29. 


Mechanical  Stokers 

The  object  of  the  mechanical  stoker  is  to  perform  the  work  that 
is  done  by  the  human  stoker  more  uniformly,  and,  in  addition,  with- 
out the  continual  opening  of  the  furnace  doors  that  are  necessary  with 
hand  firing.  It  was  explained  in  previous  pages  that  the  air  entering 
a  furnace  above  that  required  for  actual  combustion  has  to  be  raised 
to  the  temperature  of  the  hot  gases,  abstracting  a  certain  quantity  of 
heat  from  the  hot  gases  in  the  process.  When  the  furnace  door  is 
frequently  opened  a  certain  quantity  of  cold  air  passes  into  the 
furnace  each  time,  and  this  air  not  only  has  to  be  heated  to  the  same 
temperature  as  the  other  gases,  but  it  has  the  same  effect,  in  a  minor 
degree,  as  throwing  water  upon  burning  fuel — it  tends  to  clamp 
the  fire.  Hence  properly  designed  mechanical  stokers  should  avoid 
the  undoubted  heat  losses  from  this  cause.  It  is  found  also  that 
with  mechanical  stokers  very  much  lower  grades  of  fuel  can  be 
employed ;  and  further,  when  combined  with  one  of  the  systems  of 


6    STEAM   BOILERS,  ENGINES,  AND  TURBINES 


ail 


BOILER  ACCESSORIES  117 

mechanical  draught,  a  larger  quantity  of  fuel  can  be  burned  in  a 
given  time.  It  is  also  claimed  for  mechanical  stokers  that  they 
provide  smokeless  combustion.  The  ordinary  rate  of  combustion  with 
chimney  draught  is  in  the  neighbourhood  of  15  Ibs.  of  fuel  per  square 
foot  of  grate  area.  With  mechanical  stokers  and  with  mechanical 
draught,  it  is  claimed  that  the  rate  of  combustion  can  be  raised  to  as 
much  as  60  Ibs.  per  square  foot  of  grate  area.  It  must  be  understood, 
however,  that  the  rate  of  combustion  will  vary  with  the  class  of  fuel, 
and  that  increased  draught,  and  the  absence  of  admission  of  cold  air, 
will  increase  the  rate  of  combustion  of  every  class  of  fuel. 


Forms  of  Mechanical  Stoker 

Mechanical  stokers  may  be  divided   broadly  into  two  classes, 
known  as  over-feed  and  under-feed.     The  names  practically  describe 


P  ROC  TO  R/S 

PATENT  SHOVEL  STOKER  6- MOVING   FIRE  BARS, 


I}.  30.— Longitudinal  and  Transverse  Section  of  Lancashire  Boiler  fitted  with  Proctor's  Shovel 
Mechanical  Stoker.  The  Coal  is  fed  from  the  Hoppers  into  the  Boxes  below,  and  is  thenoe 
ejected  on  to  the  Fire  Bars  by  the  action  or  the  Swinging  Shovel. 


them.  In  the  over-feed  stoker  the  fuel  is  delivered  from  above,  on 
to  the  upper  surface  of  the  furnace  bars.  In  the  under-feed  stokers, 
the  fuel  is  brought  from  below,  and  is  worked  up  through  openings 
between  the  bars,  as  will  be  explained,  on  to  their  upper  surfaces. 

All  over-feed  mechanical  stokers  also  are  broadly  divided  into 
two  classes,  known  as  coking  and  sprinkling.  Some  forms  combine 
the  two.  The  broad  distinction,  however,  is,  in  the  coking  stoker  the 


ii8    STEAM   BOILERS,  ENGINES,   AND   TURBINES 


fuel  is  delivered  in  small 
quantities  periodically  on 
to  the  dead  plate,  or  the 
front  of  the  furnace  bars, 
and  is  there  allowed  to 
form  into  a  pasty  mass, 
coking  together  very  much 
in  the  same  manner  as  small 
coal  does  in  a  coke  oven. 
After  it  has  coked,  it  is 
pushed  forward  on  to  the 
front  of  the  furnace  bars, 
another  charge  taking  its 
place  at  the  coking  posi- 
tion, and  it  is  gradually 
pushed  forward  as  each 
charge  enters  the  furnace, 
and  finally  is  usually  ejected 
into  a  chamber  at  the  back 
of  the  furnace. 

In  the  sprinkler  stoker, 
small  quantities  of  fuel  are 
thrown  on  to  the  furnace 
bars  at  intervals,  the  fuel 
being  sprinkled  over  the 
whole  width  of  the  bars, 
and  the  whole  burning  mass 
being  gradually  worked  for- 
ward by  motions  of  the 
furnace  bars. 

In  all  forms  of  mechani- 
cal stokers  there  is  a  hopper 
holding  about  3  cwts.,  con- 
veniently fixed  in  front  of 
the  furnace,  at  different 
heights,  according  to  whether 
the  stoker  is  over-feed  or 
under-feed,  and  the  fuel  is 
delivered  into  the  hoppers 
by  conveyors,  and  occasion- 
ally by  hand.  The  bottoms 
of  the  hoppers  all  have 
valves,  or  other  arrange- 
ments controlling  the  ad- 
mission of  fuel  to  the 


BOILER   ACCESSORIES 


119 


furnace.  In  the  sprinkler  stoker  the  fuel  is  cast  on  to  the  fire  bars 
by  the  action  of  what  is  termed  the  shovel.  One  form  is  shown 
clearly  in  Eig.  30,  which  is  a  section  of  the  Proctor  mechanical 
stoker.  The  shovel,  it  will  be  seen,  is  a  plate  hinged  above,  and 
worked  either  by  a  spring  or  a  cam,  or  other  arrangement.  A  charge 
of  fuel  is  delivered  in  front  of  the  shovel,  and  at  stated  intervals, 
which  can  be  regulated  from  the  front  of  the  boiler,  the  shovel  plate 
moves  quickly  forward,  and  throws  the  fuel  in  a  shower  on  to  the 
furnace  bars.  In  the  Proctor  stoker  the  shovel  moves  radially.  In 
other  forms  it  moves  merely  horizontally.  In  one  form,  the  Hender- 
son, there  is  a  revolving  shovel,  shown  in  Fig.  31.  In  all  forms  of 
sprinkler  stokers  it  is  arranged  that  the  fuel  shall  be  thrown  to 
different  parts  of  the  furnace,  by  varying  the  throw  of  the  shovel, 
this  being  accomplished  by  the  action  of  the  gearing  on  the  outside. 
Thus,  taking  the  grate  bars  as  six  feet  in  length,  one  throw  would 
be  nearly  to  the  end  of  the  bars,  another  one  to  about  4^  feet, 
another  to  about  3  feet,  and  so  on.  Plate  SA  shows  a  Proctor's 
mechanical  stoker  complete. 

The  coker  stokers  are  all  fitted  with  some  form  of  ram,  or  pusher, 
as  it  is  sometimes  called,  which  pushes  the  fuel  usually  from  the  dead 
plate  on  to  the  front  of  the  bars,  the  moving  bars  carrying  it  forward. 

It  is  claimed  for  the  coker  stoker,  that  the  green  gases,  as  they 


FIG.  32. — Section  of  Barn  and  Hopper  of  Meldrum's  Coker  Stoker. 

are  termed,  the  hydrocarbons,  and  the  coal  dust  which  comes  away 
freely  from  freshly  fed  coal,  has  to  pass  over  the  mass  of  burning 


120    STEAM   BOILERS,   ENGINES,  AND   TURBINES 

coal  in  front  of  it,  and  is  consumed,  and  therefore  there  is  no 
tendency  for  it  to  make  smoke.  Fig.  32  shows  a  section  of  the  ram 
and  hopper  of  Meldrum's  coker  stoker. 


The  Grate  Bars  of  Over- Feed  Stokers 

The  grate  bars  of  over-feed  stokers  are  arranged  on  two  main 
lines.     In  one  form — in  which  are  included  the  Bennis,  the  Proctor, 


THE  MECHANISM  OF  THE  WILKINSON  STOKER. 


FIG,  33.— Mechanism  of  the  Wilkinson  Mechanical  Stoker.     The  Bars  are  arranged 
as  Steps,  as  shown,  Steam  passing  out  through  the  ends  of  the  Bars. 

the  Vicars,  the  Hodgkinson — the  bars  stand  side  by  side,  and  alternate 
bars  are  moved  upwards  and  forwards  at  intervals,  returning  to  their 
normal  positions  when  the  other  bars  move  forward,  this  motion  of 
the  bars  giving  the  forward  motion  to  the  fuel.  In  another  type 
of  the  straight-bar  stokers,  the  bars  are  given  a  jerking  motion  at 
intervals,  which  has  the  same  effect. 

The  furnace  bars  are  also  sometimes  all  moved  forward  together, 
and  withdrawn  singly,  and  in  other  forms  moved  forward  singly,  and 
withdrawn  together.  In  some  forms  of  stoker  also— notably  the 
Bennis,  and  the  Wilkinson,  an  American  stoker — the  grate  bars,  or 
a  portion  of  them,  are  made  hollow,  and  a  steam  jet  is  fixed  at  the 
front  of  each  bar,  the  air  supply  to  the  furnace  being  furnished  by 


BOILER   ACCESSORIES 


121 


JAMES   HODOKINSON, 
WEST  MIQH   »T«etT  MACHINE   WORKS 


FIG.  34.— Transverse  and  Longitudinal  Section  of  Hodgkinson's  Mechanical  Stoker. 


FIG.  35.— Longitudinal  Section  of  a  Mechanical  Stoker  fitted  to  a 
Lancashire  Boiler, 


122     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  steam  jets,  and  therefore  the  bars  themselves.  It  is  claimed  for 
this  arrangement,  that  the  bars  can  be  fixed  very  close  together,  so 
that  very  small  fuel  can  be  burned,  and  that  the  draught  is  evenly 
distributed  over  the  whole  of  the  furnace,  and  is  under  control,  by 
the  steam  jets.  In  some  forms  of  this  apparatus  the  steam  jet  is 
automatically  controlled  by  the  output  of  the  boiler.  When  the 
boiler  is  furnishing  steam  rapidly,  the  steam  jet  passes  a  comparatively 
large  quantity  of  steam,  and  vice  versa. 

In  the  Wilkinson  Stoker  also,  as  will  be  seen  from  Fig.  33, 
the  fire  bars  are  made  in  the  form  of  steps,  inclined  downwards 
towards  the  back  of  the  furnace,  alternate  bars  being  moved  to  and 
fro,  as  explained  above,  and  the  fuel  is  carried  down  from  step  to 
step,  to  an  ash  table  at  the  bottom,  where  the  whole  of  its  com- 
bustible matter  is  finally  consumed,  and  the  remainder  then  passes 
over  on  to  the  ash  slide  shown,  between  the  ash  table  and  the  fire 
bridge,  and  is  allowed  to  fall  into  the  ashpit  periodically,  by  with- 
drawing the  slide.  In  this  furnace  also  there  is  a  fire-brick  arch 
over  the  front  portion. 

In  the  Bennis  stoker  the  bars  are  inclined  upwards  towards  the 
back  of  the  furnace,  and  the  fuel  travels  up  the  incline,  and  is  then 
tipped  over  into  the  chamber  at  the  back,  as  explained.  Fig.  34 
shows  the  Hodgkinson's  mechanical  stoker,  and  Fig.  35  another 
form. 

The  Auto  Stoker 

This  apparatus,  which  presents  certain  features  that  are  of 
interest,  and  is  made  by  the  Union  Ironworks  Co.  of  Ashton-under- 


FIG.  36. — Longitudinal  and  Transverse  Sections  of  the  "Auto"  Stoker. 

Lyne,  is  shown  in  Fig.  36.  There  are  the  usual  hoppers  over  the 
furnaces,  from  which  the  coal  passes  on  to  the  fire  bars,  but  the 
hoppers  are  supplied  from  bunkers  in  the  boiler-room,  by  the  bucket 


BOILER   ACCESSORIES  123 

elevators  shown,  which  deliver  the  coal  to  the  shoots  above  the 
hoppers. 

The  bunkers  are  placed  in  the  position  where  coal  is  usually 
heaped  for  hand  firing,  and,  as  will  be  seen,  if  anything  happens  to 
the  automatic  gearing,  hand  firing  can  be  immediately  resorted  to, 
the  bunkers  having  the  slides  shown,  at  the  foot,  through  which  coal 
can  be  taken  by  the  firemen. 

The  fire  bars  are  of  the  special  form  shown,  and  the  coal  is  first 
pushed  by  the  ram  from  the  feed  box  on  to  the  convex  portion  of  the 
bars.  From  the  convex  portion  of  the  bars,  the  fuel  passes  forwards, 
carried  by  the  motion  of  the  bars,  and  a  mass  of  fuel  at  a  very  high 
temperature  is  formed  in  the  concave  portion  just  beyond,  the  hydro- 
carbons and  dust  brought  in  with  the  fuel  having  to  pass  over  this 
hot  zone,  and,  it  is  claimed,  being  completely  burnt. 

The  ashes  and  clinkers  are  pushed  over  the  ledge  at  the  back  of 
the  furnace,  in  the  manner  described  in  connection  with  other  forms 
of  mechanical  stokers. 

All  the  fire  bars  move  to  and  fro,  but  only  four  of  the  bars  in 
each  apparatus  receive  motion  directly  from  the  driving  shaft.  The 
remaining  bars  are  keyed  to  the  four  driving  bars,  and  receive  motion 
from  them. 

The  four  bars  are  driven  by  short  connecting  rods  from  a  crank 
shaft  in  front  of  the  boiler. 


Vicars  Mechanical  Stoker 

In  the  Vicars  mechanical  stoker,  a  sectional  drawing  of  which 
is  shown  in  Fig.  37,  there  are  the  usual  hoppers,  and  the  coal 
passes  from  them  into  boxes,  usually  two  for  each  Hue  of  a  Lancashire 
boiler,  from  which  it  is  pushed  by  reciprocating  plungers  or  rams, 
working  alternately,  on  to  the  dead  plate,  where  it  is  allowed  to 
remain  for  a  short  time,  to  facilitate  coking.  From  the  dead  plate 
it  is  pushed  on  to  the  moving  fire  bars,  where  it  is  carried  forward 
in  the  usual  way  by  their  motion.  The  arrangements  at  the  back 
of  the  furnace  are  a  little  different  to  those  in  some  of  the  other 
stokers :  the  fire-brick  bridge  is  built  a  little  distance  back  from  the 
ends  of  the  fire  bars,  and  the  fuel  is  allowed  to  fall  over  in  a  mass 
on  the  bottom  of  the  flue,  as  shown  in  the  drawings,  so  that  no 
air  can  pass  from  the  under  side  of  the  bars  to  the  front  of  the 
furnace.  The  space  between  the  bridge  and  the  front  of  the  fire  bars 
forms  the  usual  combustion  chamber,  and  the  clinkers  are  removed 
at  intervals.  The  whole  of  the  fire  bars  move  forward  together,  and 
alternate  bars  are  moved  backwards  at  intervals,  it  being  claimed 
that  this  action  is  best  for  carrying  the  fuel  forward. 


124    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

For  water-tube  boilers  the  arrangement  is  slightly  different.  There 
is  a  second  set  of  inclined  bars,  on  to  which  the  fuel  falls  from  the 
end  of  the  fire  bars,  and  it  is  gradually  pushed  from  them  forward 
into  the  pit  below,  a  mass  of  burning  fuel  accumulating  there, 
preventing  the  passage  of  any  air  past  it  to  the  front  of  the  furnace, 
from  below,  and  providing  the  combustion  chamber. 


FIG.  37.— Longitudinal  Section  of  Lancashire  Boiler  fitted  with  Vicars  Mechanical 

Stoker. 

The  stroke  of  the  plungers  forming  the  feed  can  be  regulated 
from  the  front  of  the  boiler  at  will,  and  also  the  stroke  of  the  fire 
bars.  The  whole  of  the  feeding  plant  is  supported  from  the  floor, 
and  not  from  the  front  of  the  boiler. 


Chain-Grate  Stokers 

In  the  other  type  of  over-feed  stoker,  the  furnace  bars  are  made 
in  the  form  of  an  endless  chain,  the  bars  forming  links  of  the  chain, 
and  the  chain  itself  passing  over  drums  at  the  front  and  back  of  the 
furnace.  The  chain  is  kept  continually  in  motion  by  the  revolution 
of  the  front  drum,  this  causing  the  forward  motion  of  the  fuel.  The 
fuel  is  delivered  from  the  hopper  on  to  the  furnace  bars  immediately 


BOILER  ACCESSORIES 


125 


below  it,  over  the  whole  width,  the  amount  of  the  feed  being  regu- 
lated by  valves  or  doors  at  the  bottoms  of  the  hoppers,  lifting  verti- 
cally at  certain  periods,  as  with  the  other  forms.  The  fuel  travels 
slowly  forward  as  the  grate  moves,  and  the  ash  and  clinker  is  delivered 
to  a  chamber v  at  the  back,  as  in  other  forms.  The  front  drum  is 
driven  by  worm  and  wheel  gearing,  with  a  ratchet  and  pawl  attach- 
ment, by  means  of  which  the  rate  of  travel  of  the  grate  can  be  adjusted, 
and  the  height  to  which  the  valve  or  lifting  fire  door  moves,  can  also 
be  adjusted. 

In  the  Babcock  and  Wilcox  chain-grate  stoker  which  is  shown 
in  Plates  SB  and  c,  the  whole  apparatus  is  arranged  to  run  on  rails 
into  the  furnace  space  in  the  Babcock  boiler.  The  rails  which  are 
shown  in  the  illustrations,  accommodate  the  wheels  of  the  truck 
forming  the  carriage  of  the  stoker,  and  the  whole  thing  can  be  run 
out  at  any  moment  for  repair  and  quickly  run  in  again.  It  is  claimed 
that  repairs  can  be  made  to  the  grate,  however,  without  moving  the 
stoker  out  of  its  place,  by  merely  running  the  chain  back  till  the 
defective  bar  is  exposed.  Plate  TB  shows  a  pair  of  water-tube 
boilers  fitted  with  another  form  of  chain  grate  stokers,  in  which  the 
links  are  half  the  width  of  the  stoker. 


Under- Feed  Stokers 

In  the  under-feed  stoker,  as  explained,  the  fuel  is  contained  in  a 
magazine  or  reservoir,  as  shown  in  Figs.  38  and  39,  carried  under  the 


FIG.  38.— Transverse  Section  of  Underfeed  Mechanical  Stoker.  Q  is  the  Magazine 
for  the  Fuel;  PP  are  Hot-air  Channels;  SS  are  the  passages  for  the  Air  under 
the  Fire  Bars,  FF.  The  Fuel  is  forced  up  at  RR  on  to  the  Bars. 

apparatus  corresponding  to  the  furnace  grate  in  other  forms  of  furnace, 
and  communicating  with  the  hopper,  as   shown  in  Fig.  39.      The 


126    STEAM  BOILERS,  ENGINES,  AND  TURBINES 

furnace  bars  are  different  from  those  usually  employed,  and  one  firm 
of  makers  of  under-feed  stokers  claims  that  they  have  no  grate. 
There  is,  however,  in  both  forms  on  the  market  an  apparatus  corre- 
sponding to  a  grate  type,  and  the  fuel  is  forced  out  through  spaces 
between  the  bars,  of  which  the  grate  or  its  equivalent  is  com- 
posed, on  to  the  sides,  and  the  ash  is  carried  off  in  the  usual  way. 
There  are  two  methods  employed  for  forcing  the  fuel  up  through  the 
furnace  bars.  In  the  "  Erith  "  grateless  under-feed  stoker  a  ram  is 
employed,  combined  with  a  rod  attached  to  the  front  of  the  ram,  and 
carrying  wedge-shaped  blocks,  designed  to  give  a  lifting  movement 
to  the  fuel.  The  ram  is  moved  forward  periodically  by  the  steam 


FIG.  39. — Longitudinal  Section  of  Underfeed  Stoker,  showing  the  Ram,  which  forces 
the  Fuel  up  between  the  Bars,  also  the  Air  Duct  and  the  Hopper.  A  is  the 
Hopper ;  F,  the  Fire  Bars ;  Q,  the  Fuel  Magazine. 

piston  in  the  engine  cylinders  to  which  it  is  attached,  a  certain 
quantity  of  fuel  being  pushed  on  to  the  furnace  bars,  or  the  dead 
plates,  as  the  Erith  Company  prefer  to  call  them,  at  each  stroke. 
In  one  form  of  the  Under-Feed  Stoker  Co.'s  apparatus,  the  fuel  is 
carried  forward  by  an  Archimedean  screw,  the  screw  being  worked  by 
gearing  from  any  convenient  source  of  power,  or  by  a  motor  or  steam 
cylinder,  and  in  another  form  by  a  ram,  as  shown  in  Fig.  39.  The 
continuous  motion  of  the  Archimedean  screw  forces  the  fuel  forwards, 
and  at  the  same  time  upwards  through  the  furnace  bars.  In  both 
forms  of  under-feed  stokers,  air  is  admitted  to  the  fuel  from  under- 
neath, by  means  of  what  are  virtually  tubes,  or  tuyeres,  in  the 


BOILER  ACCESSORIES  127 

furnace  bars  themselves.  In  the  Erith  stoker  there  is  an  air-chamber 
underneath  the  fuel  magazine,  to  which  air  is  brought  by  fan,  or 
other  means,  and  ib  is  passed  from  it  through  the  hollows  in  the 
dead  plates,  up  into  the  fuel.  In  the  Under-Feed  Stoker  Co.'s  appa- 
ratus, the  lower  portion  of  the  magazine  itself  forms  an  air-chamber, 
and  the  air  is  forced  up  between  the  grate  bars.  It  is  claimed  in 
both  cases  that  the  air  consumption  and  fuel  consumption  are  under 
complete  control,  from  the  front  of  the  boiler,  in  the  usual  way. 


Providing  the  Air  for  the  Furnace 

There  are  four  methods  of  providing  the  air  that  is  required  by 
the  furnace — by  chimney  draught,  by  forced  draught,  by  induced 
draught,  and  by  the  aid  of  steam  jets.  All  of  the  methods  are 
simply  variations  of  the  same  thing.  In  all  of  them  a  certain  force 
is  applied  to  the  air,  to  drive  it  through  the  fire  bars,  the  fuel  lying 
on  them,  and  the  flues,  etc.,  beyond.  With  forced  and  induced 
draught  the  air  is  under  much  greater  control.  With  chimney 
draught  the  only  method  of  control  is  by  closing  or  opening  the 
damper,  more  or  less  throttling  the  supply  of  air. 


Chimney  Draught 

Chimney  draught  is  caused  by  the  difference  in  the  weight  of  the 
column  of  hot  gases  in  the  chimney,  and  that  of  a  similar  column  of 
air  on  the  outside  of  the  chimney.  Perhaps  the  matter  will  be  more 
easily  understood  by  reference  to  the  case  of  the  ventilation  of  a  coal 
mine.  At  the  present  time  furnace  ventilation  is  not  often  found  in 
coal  mines,  but  thirty  years  ago  it  was  very  common.  Now  the 
furnace  has  been  almost  entirely  displaced  by  fans,  very  much  in  the 
same  way  that  chimney  draught  for  boilers  is  gradually  being  dis- 
placed by  one  or  other  of  the  methods  mentioned.  In  a  coal  mine 
there  are  two  vertical  shafts,  from  the  surface  to  the  coal  seam,  a 
short  distance  apart,  and  at  the  bottom  of  the  shafts  there  are  roads 
extending  into  the  mine  from  each  of  the  shafts,  the  roads  being  con- 
nected by  cross-roads,  working  places,  etc.,  and  for  ventilation  the 
air  has  to  pass  down  one  of  the  shafts,  called  the  down-cast,  along 
the  road  leading  from  it,  through  the  cross-roads,  working  faces,  to 
the  road  leading  to  the  other  shaft,  known  as  the  up-cast,  and  through 
the  up  cast  to  the  surface  again.  In  the  days  of  furnace  ventilation, 
a  large  furnace  was  kept  continually  burning,  near  the  bottom  of  the 
up-cast  shaft,  the  furnace  being  very  similar  to  that  of  a  boiler 
furnace,  but  without  boiler  flues,  etc.,  and  its  office  was  to  heat  the 


128    STEAM  BOILERS,  ENGINES,   AND  TURBINES 

return  air  from  the  mine,  and  to  provide  a  column  of  hot  air  in  the 
up-cast  shaft,  the  difference  between  the  weight  of  this  column  of  air 
and  that  of  the  column  of  air  in  the  down -cast  shaft,  which  was  at 
the  temperature  of  the  outside  atmosphere,  providing  what  was  called 
the  motive  column. 

Air,  it  will  be  remembered,  has  weight,  and  when  it  passes  over 
the  surface  of  the  flues,  through  fire  bars,  the  interstices  of  coal,  etc., 
it  creates  friction,  and  this  necessitates  the  expenditure  of  a  certain 
force  to  move  it.  Further,  the  weight  of  a  given  volume  of  air  varies 
directly  with  its  absolute  temperature.  At  32°  F.,  1  Ib.  of  air 
occupies  approximately  12^  cubic  feet ;  at  double  the  absolute  tem- 
perature, or  about  525°  F.,  the  same  weight  of  air  would  occupy  25 
cubic  feet.  The  absolute  temperature  corresponding  to  32°  F.,  it  will 
be  remembered,  is  493°  F.,  absolute  zero  being  461°  F.  below  the  zero 
of  Fahrenheit's  scale ;  consequently  double  the  absolute  temperature 
at  32°  F.  is  986°  absolute  Fahrenheit,  corresponding  to  525°  gauge 
temperature  Fahrenheit. 

With  the  arrangements  of  a  boiler  furnace,  flues,  chimney,  etc., 
the  property  of  fluid  pressure  that  has  been  referred  to  in  a  previous 
portion  of  this  chapter  comes  into  play.  It  will  be  remembered  that 
in  a  fluid  any  pressure  communicated  to  any  part  of  the  fluid  is  trans- 
mitted through  the  fluid  in  all  directions.  In  the  case  of  the  boiler 
furnace,  the  air  passes  through  the  ashpit  and  the  fire  bars  into  the 
coal,  and  it  is  the  weight  of  the  column  of  air  above  the  entrance  to 
the  ashpit  which  causes  the  air  to  move  into  and  through  the  furnace. 
If  the  hot  gases  met  a  similar  column  of  air  on  the  other  side  of  the 
boiler,  the  pressure  on  the  two  sides  would  be  equal,  and  there  would 
be  no  force  tending  to  move  the  air  and  the  gases  through  the  furnace. 
But  by  the  provision  of  a  column  of  hot  gases,  such  as  exists  in  a 
boiler  chimney,  and  whose  weight  is  less  than  that  of  the  column  of 
air  pressing  against  the  ashpit  entrance,  there  is  a  force  tending  to 
cause  the  air  to  pass  into  the  ashpit,  and  thence  through  the  fire  and 
flues,  etc.,  this  force  being  measured  by  the  difference  between  the 
weight  of  the  column  of  hot  gases  in  the  chimney,  and  that  of  the 
equivalent  column  of  air  outside  the  ashpit. 

It  will  be  evident  from  the  above,  that  the  larger  the  area  of  the 
chimney,  and  the  greater  the  height  of  the  chimney,  the  greater  is 
the  force  tending  to  move  the  air  into  the  furnace,  and  to  move  the 
hot  gases  through  the  furnace  flues.  Further,  it  is  evident  that  the 
higher  the  temperature  of  the  hot  gases  in  the  chimney,  the  greater  is 
the  difference  between  their  weight  and  that  of  the  column  of  air 
outside,  and  therefore  the  greater  is  the  force  moving  the  air  and  hot 
gases  or,  as  it  is  expressed,  creating  a  draught.  On  the  other  hand, 
it  will  easily  be  understood  that  whatever  quantity  of  heat  is  left  in 
the  hot  gases,  when  they  enter  the  chimney,  is  wasted,  so  far  as 


PLATE   SA. — Front  View   of    Proctor's   Mechanical   Stoker,   as  fitted  to  the   Two 
Furnaces  of  a  Lancashire  Boiler. 


PLATE  SB.— Front  View  of  Babcock  &  Wilcox  Chain  Grate  Stoker. 


PLATE  8c. — View  of  Babcock  &  Wilcox  Chain  Grate  Stoker  from  the  back. 

[To  face  p.  128. 


BOILER  ACCESSORIES 

heating  the  water  and  the  steam  in  the  boiler  is  Concerned.  The 
standard  temperature  at  which  the  hot  gases  are  usually  delivered  to  the 
chimney  is  in  the  neighbourhood  of  600°.  There  is  a  limiting  value 
to  the  temperature  at  which  the  hot  gases  are  delivered  to  the  chimney, 
for  the  following  reason.  Though  the'  density  of  the  gases  decreases 
in  direct  proportion  to  the  absolute  temperature,  the  velocity  at  which 
they  pass  through  the  chimney  increases  as  the  square  root  of  the 
absolute  temperature,  and  the  limiting  value — the  economic  tempera- 
ture— is  found  to  be  550°  F.  above  the  temperature  of  the  atmosphere. 
As  the  average  in  this  country  is  in  the  neighbourhood  of  60°,  this 
means  that  the  limiting  temperature  is  in  the  neighbourhood  of 
600°  F.  It  is  the  velocity  at  which  the  gases  pass  up  the  chimney, 
which  controls  the  intensity  of  the  draught.  The  force  required  to 
drive  the  air  through  the  boiler  furnace,  and  to  drive  the  hot  gases 
through  the  boiler  Hues  and  up  the  chimney,  because  some  force  is 
expended  even  in  overcoming  the  friction  of  the  hot  gases  on  the 
walls  of  the  chimney,  both  in  mines  and  in  boiler  furnaces,  is 
measured  by  a  special  apparatus,  known  as  a  water-gauge,  the  force 
being  described  as  so  many  inches  of  water-gauge.  One  inch  of 
water-gauge  corresponds  to  0'578  oz.  pressure  per  square  inch,  and  is 
arrived  at  in  the  following  manner.  The  weight  of  a  cubic  foot  of 
water  is  62*355  Ibs.,  at  62°  F.,  and  consequently  that  is  the  pressure 
exerted  by  a  cubic  foot  of  water  upon  an  area  of  one  square  foot. 
The  weight  of  a  mass  of  water  1  square  foot  in  area  and  1  inch  in 

62*355 
depth  is  — r-ft  —  =  5*197  Ibs.,  and  the  weight  of  a  cubic  inch  of  water 

will  be  the  weight  of  this  last  quantity — 5*197  Ibs.  divided  by  144 
(the  number  of  square  inches  in  a  square  foot)  =  0*578  oz,,  and  this  is 
therefore  the  pressure  which  1  square  inch  of  water  exerts  upon  the 
square  inch  base  it  stands  upon,  and  is  the  value  of  the  inch  water- 
gauge. 

NOTE. — The  inch  water-gauge  must  not  be  confused  with  the 
miner's  inch,  which  is  something  quite  different,  and  has  nothing  to 
do  with  pressures. 

The  water-gauge  usually  consists  of  a  U'tube,  having  a  scale 
representing  the  difference  of  level  between  the  two  legs,  reduced  to 
inches  of  water.  The  two  legs  are  arranged  to  be  open  to  the  two 
atmospheres,  or  the  atmosphere  and  the  body  of  gas,  the  difference  of 
pressure  between  which  it  is  desired  to  measure.  There  are  different 
methods  of  accomplishing  this,  rubber  tubes  slipped  over  the  ends  of 
the  legs  of  the  tube,  being  a  simple  and  favourite  one.  One  simple 
arrangement  is,  the  (j-tube  is  fixed  on  a  piece  of  board,  or  in  any 
convenient  position,  in  one  body  of  gas,  say  in  the  atmosphere,  and  a 
short  tube  is  led  from  the  end  of  one  leg,  through  an  aperture 
provided  for  the  purpose,  in  a  partition  dividing  the  two  bodies  of 

K 


130    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

gas,  into  the  other  body,  the  second  leg  being  open  to  the  atmosphere 
where  the  gauge  is  fixed. 

Evidently  the  difference  between  the  pressures  of  the  two  vessels, 
or  the  two  air  passages,  or  an  air  passage  and  the  atmosphere,  will  be 
measured  by  the  height  of  the  water  in  the  gauge.  It  is  of  course 
not  necessary  that  the  water  shall  be  1  square  inch  in  section.  It 
may  be  of  any  sectional  area,  provided  it  is  graduated  accordingly. 

For  ordinary  boiler  work,  pressures  up  to  2J  inches  water-gauge  are 
employed,  and  of  the  total  pressure  required,  the  fuel  takes  from 
0'2  up  to  1*8  inch  of  water-gauge,  according  to  the  substance.  The 
following  table,  given  by  Mr.  Hutton,  shows  the  draught  required  for 
the  different  kinds  of  fuel.  As  will  be  seen,  straw,  wood,  and  the 
free  burning  coals  require  the  smallest  pressure  to  drive  the  air 
through  them,  large  coal  also  requires  a  small  pressure  compared 
with  small  coal,  and  the  anthracites  require  the  largest  pressure  of  all. 


TABLE  XIV. 


Kind  of  fuel. 


Pressure  required  in  inches, 
water-gauge. 

.     0-2 

.     0-3 

.     0-35 

.     0-4 

.     0-5 

.     0-6 

.     0-4  to  0-7 

.     0-6 

0-9 

.     0-7 

1-1 

.     0-8 

1-1 

.     0-9 

1-2 

.     1-0 

1-3 

.     0-2 

1-4 

.     1-2 

1-5 

.     1-3 

1-8 

Straw. 
Wood . 
Sawdust 
Peat  (light) 

,,     (heavy) 
Sawdust  mixed  with  small  coal 
Steam  coal  (round) 
Slack  (ordinary). 

„      (very  small) 
Coal  dust    . 
Semi-anthracite  coal 
Mixture  of  breeze  and  slack 
Anthracite  (round) 
Mixture  of  breeze  and  coal  dust 
Anthracite  slack  . 


It  was  mentioned  in  the  first  chapter,  that  a  certain  quantity  of 
oxygen  is  required  for  the  complete  combustion  of  every  kind  of 
fuel,  and  it  may  be  mentioned  that  the  minimum  quantity  of  air 
required  to  furnish  the  oxygen  for  the  complete  combustion  of  1  Ib. 
of  carbon,  oxidizing  to  carbonic  acid,  is  approximately  12  Ibs.  In 
practice,  however,  it  is  never  possible  to  work  to  exactly  these 
conditions,  and  it  is  usual  to  reckon  upon  a  supply  of  24  Ibs.  of  air 
to  each  pound  of  the  fuel  to  be  consumed. 

The  volume  of  the  gases  produced  from  the  combustion  of  carbon, 
providing  that  it  is  completely  oxidized  to  carbonic  acid,  is  the  same 
as  that  of  the  air,  before  the  carbon  combined  with  the  oxygen,  at 
the  same  temperature.  The  volume  of  the  nitrogen,  at  any  given 
temperature,  remains  unchanged  of  course ;  and  the  volume  of  the 
carbonic  acid  formed  by  the  combination  of  the  carbon  with  the 


BOILER   ACCESSORIES  131 

oxygen,  is  practically  the  same  as  that  of  the  oxygen  before  it  entered 
into  combination,  always  providing  the  temperatures  are  the  same. 
Hence  the  volume  of  the  hot  gases  is  practically  the  same  as  the 
volume  of  the  air  supplied  to  the  furnace,  and  the  whole  of  the  gases, 
consisting  of  the  carbonic  acid  formed,  the  unchanged  nitrogen  and 
oxygen,  have  to  be  raised  to  the  same  temperature,  the  result  being 
that  the  temperature  at  which  the  hot  gases  leave  the  burning  fuel 
is  never  greater  than  about  2400°  F.,  instead  of  being  in  the  neigh- 
bourhood of  4000°  F. 

Chimneys  are  required  for  two  purposes — to  furnish  the  neces- 
sary draught,  and  also  to  carry  off  the  products  of  combustion, 
the  hot  gases,  etc.,  and  to  deliver  them  to  the  atmosphere  at  a  height 
where  they  will  do  little  harm.  When  the  chimney  is  employed 
only  for  delivering  the  products  of  combustion  harmlessly  into  the 
neighbouring  atmosphere,  it  is  evident  that  the  height  of  the  chimney 
may  be  very  much  less  in  a  great  many  instances,  than  where  it  is 
also  required  to  furnish  the  necessary  draught,  and  one  reason  why 
chimney  draught  is  being  superseded  by  the  other  forms  of  draught, 
in  places  where  comparatively  low  chimneys  may  be  fixed,  is  because 
the  cost  of  the  chimney  itself  is  often  a  serious  item  in  the  outlay, 
and  because  the  chimney  demands,  for  furnishing  the  draught, 
something  like  25  per  cent,  of  the  total  energy  delivered  to  the  hot 
gases  at  the  furnace.  It  will  be  understood  that  the  heat  carried  by 
the  hot  gases  is  measured  by  the  product  of  their  weight  into  their 
temperature,  and  into  their  specific  heat,  and  as  they  set  out  with  a 
temperature  of  2400°  F.,  and  are  delivered  to  the  chimney  at  600°  F., 
25  per  cent,  of  their  energy  is  used  in  the  chimney ;  whereas  if  the 
chimney  was  merely  an  apparatus  to  deliver  the  hot  gases  harmlessly, 
the  only  expenditure  of  energy  necessary  in  the  chimney  would  be 
that  required  to  overcome  the  friction  of  the  hot  gases  on  the  sides 
of  the  chimney.  The  waste  involved  in  delivering  the  gases  to  the 
chimney  at  600°  F.  may  be  better  appreciated  by  converting  the  heat 
units  which  they  carry  into  mechanical  energy.  There  is  hardly 
space  to  reproduce  the  calculation  involved,  but  remembering  that 
each  unit  represents  778  foot-lbs.  of  work,  and  that  each  pound  of  the 
gas  carries  off  approximately  143  heat  units,  the  enormous  amount 
of  energy  passing  up  a  chimney  will  easily  be  understood.  It  has 
been  computed  that  the  actual  work  done  by  the  hot  gases,  in  creating 
the  draught,  is  only  0'00056  of  the  amount  of  energy  contained  in 
the  gases  themselves. 

Sizes  of  Chimneys  and  Horse- Power  of  Boilers 

The  chimney  designed  to  furnish  draught  for  a  boiler,  or  battery 
of  boilers,  has  two  sets  of  dimensions,  both  of  which  are  equally 


132    STEAM  BOILERS,  ENGINES,  AND   TURBINES 

important.  Its  sectional  area  must  be  sufficient  to  allow  the 
whole  of  the  gases  delivered  by  the  boiler,  or  battery  of  boilers,  to 
escape  freely  through  the  chimney,  without  throttling.  In  addition, 
if  the  chimney  is  also  to  furnish  the  draught  necessary  for  the  boilers, 
it  must  be  of  a  sufficient  height  to  furnish  the  required  motive 
column  described  on  p.  128.  The  total  ene'rgy  present  in  the  gases 
passing  through  the  chimney  will  depend  on  both  of  these  factors. 
The  larger  the  area  of  the  chimney,  and  therefore  the  larger  the 
volume  of  the  gases  passing  through  it,  the  greater  the  energy 
present  in  a  column  of  a  given  height ;  and  also  the  greater  the 
height  of  the  chimney,  the  greater  the  energy  present  for  a  given 
area.  The  H.P.  of  the  boiler,  as  it  is  sometimes  expressed,  or  the 
battery  of  boilers,  determines  the  sectional  area  of  the  chimney,  and 
this  is  quite  independent  of  the  height  of  the  chimney.  The  modern 
method  of  describing  the  capacity  of  the  boiler,  as  able  to  evaporate 
a  certain  quantity  of  water  per  hour  to  steam  at  a  certain  pressure, 
is  very  much  more  accurate,  and  more  scientific.  For  it  will  be 
evident  that  the  H.P.  furnished  by  the  steam  generated  in  any 
boiler  will  vary  with  the  engine  in  which  the  steam  is  used.  Thus, 
taking  the  consumption  of  non-condensing  engines  at  from  30  to 
40  Ibs.  of  steam  per  H.P.  per  hour,  simple  engines  condensing  at 
from  24  to  30  Ibs.,  compound  engines  at  from  18  to  25,  and  triple 
expansion  engines  at  from  15  to  20,  the  H.P.  of  a  boiler,  or  battery 
of  boilers,  could  be  stated  in  very  different  figures,  and  would  be 
furnishing  a  very  different  number  of  H.P.,  according  to  the  type  of 
engine  to  which  it  was  furnishing  steam. 

From  what  has  been  stated  on  previous  pages,  it  will  be  under- 
stood that,  in  order  that  a  certain  quantity  of  water  shall  be  raised  to 
a  certain  temperature,  and  converted  into  steam,  a  certain  number  of 
heat  units  must  be  delivered  to  it,  and  this  requires,  in  each  kind  of 
boiler,  the  consumption  of  a  certain  quantity  of  fuel,  again  varying 
with  the  composition  of  the  fuel,  this  again  requiring  a  certain 
quantity  of  air,  and  furnishing  a  certain  volume  of  heated  gases. 
This  again  implies  the  presence  of  a  certain  grate  area  in  the  furnace, 
or  furnaces,  in  which  the  fuel  is  consumed.  Hence  it  will  be  evident 
that  the  area  of  the  chimney  will  depend  upon  the  area  of  the  grate 
or  grates  on  which  the  fuel  is  burned,  to  furnish  the  hot  gases  that 
are  to  pass  through  the  chimney.  Professor  Thurston  gives  as  a 
standard  for  chimneys  of  200  feet  high  and  upwards,  a  sectional  area 
of  2  square  inches  for  each  pound  of  fuel  consumed  on  the  grates 
supplying  the  chimney ;  and  he  gives  as  a  further  standard,  the 
sectional  area  of  the  chimney  as  from  -|  to  -J-  of  the  grate  area. 

It  should  be  mentioned  en  passant,  that  this  last  standard  will  be 
subject  to  modification  where  the  chimney  is  only  employed  for 
carrying  the  gases  off  harmlessly.  As  will  be  explained,  with  all  the 


BOILER  ACCESSORIES  133 

methods  known  generically  as  mechanical  draught,  very  much  higher 
rates  of  consumption  of  fuel  are  obtained  with  a  given  grate  area 
than  are  usual  with  chimney  draught,  and  as  this  produces  a  larger 
quantity  of  hot  gases,  if  they  are  not  to  be  throttled  by  the  chimney 
the  sectional  area  of  the  latter  must  be  increased  in  proportion.  On 
the  other  hand,  where  the  chimney  is  only  employed  to  get  rid  of  the 
hot  gases,  these  will  be  at  a  much  lower  temperature  than  is  usual 
with  chimney  draught,  and  therefore  their  volume  will  be  less  from  that 
cause  than  it  would  have  been  where  the  hot  gases  create  the  draught. 


The  Factors  ruling  the  Height  of  a  Chimney 

It  has  been  explained  that  the  chimney  is  required  to  carry  a 
column  of  hot  gases  of  sufficient  size  to  furnish  the  necessary  motive 
column.  The  weight  of  the  column  of  gases  in  the  chimney,  however, 
will  depend  inversely  upon  their  absolute  temperature.  Further,  the 
velocity  of  the  gases  have  an  important  bearing  upon  the  matter,  as 
will  be  seen.  The  velocity  at  which  the  gases  pass  through  the 
chimney  rules  the  velocity  with  which  they  pass  through  the  boiler 
tubes,  or  the  space  around  the  tubes,  flues,  etc.,  and  this  again  rules 
the  rate  at  which  air  is  admitted  to  the  furnace,  and  at  which  com- 
bustion takes  place.  Hence  the  velocity  of  the  gases  in  the  chimney 
rules  the  rate  of  combustion,  this  again  being  ruled  by  the  difference 
in  the  pressure  between  the  ashpit  and  the  furnace.  Again,  the 
velocity  of  the  gases  is  ruled  by  the  difference  of  pressure  between 
the  column  of  the  atmosphere,  and  the  column  of  hot  gases  in  the 
chimney.  The  pressure  exerted  by  the  motive  column  is  known  as 
the  head,  and  is  usually  denoted  by  the  letter  H,  and  the  head  of 
any  motive  column  is  equivalent  to  the  height  through  which  the 
gases  composing  that  column  would  have  fallen  in  acquiring  the 
velocity  at  which  the  gases  are  moving.  The  velocity  at  which 
the  gases  are  moving  is  found  from  the  formula  v  =  \/2gh,  where  v 
is  the  velocity  of  the  gases,  h  is  the  height  of  the  motive  column, 
under  which  they  are  moving,  and  g  is  the  accelerating  force  of 
gravity,  taken  usually  as  32 '2  feet  per  second.  The  formula  will  be 
recognized  as  that  which  is  applied  to  all  falling  bodies.  It  will  be 
seen  from  it,  however,  that  the  velocity  of  the  gases,  the  accelerating 
force  of  gravity  being  constant,  varies  as  the  square  root  of  the  head 
of  the  motive  column.  In  mining  work  this  is  expressed  by  saying 
that  the  velocity  of  the  air  varies  inversely  as  the  square  root  of  the 
water-gauge,  and  this  may  be  applied  equally  to  boiler-work.  The 
height  of  any  column  of  any  fluid  required  to  furnish  a  given  pressure 
depends  directly  upon  the  pressure,  and  inversely  upon  the  density 
of  the  fluid. 


134    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

Here,  in  connection  with  chimney  draught,  a  very  important 
matter  comes  in,  viz.  the  temperature  of  the  air  outside  of  the 
chimney.  In  the  accompanying  table,  which  is  taken  from  the 
Sturtevant  Company's  book  on  "  Mechanical  Draught,"  the  pressures 
in  inches  of  water-gauge,  with  different  temperatures  of  the  gases  in 
the  chimney,  and  different  temperatures  of  the  outside  air,  are  given, 
the  chimney  temperatures  from  200°  to  500°  F.,  and  the  outside 
temperatures  from  0°  to  100°.  It  will  be  noted,  from  an  inspection 
of  the  table,  what  a  very  wide  difference  of  pressure  a  difference  in 
the  temperature  of  the  outside  air  makes,  as,  say,  between  a  cold 
winter  atmosphere  and  a  hot  summer  one.  The  figures  given  are 
for  a  chimney  of  100  feet  in  height.  With  the  chimney  temperature 
at  500°  F.,  it  will  be  noted  that  with  the  temperature  of  the  outside 
air  at  30°,  the  water-gauge  produced  is  0-73  inches,  while  with  the 
same  chimney  temperature,  and  with  an  outside  temperature  of  100°, 
the  water-guage  is  only  0*534,  or  a  reduction  of  0196,  sufficient  to 
furnish  the  pressure  for  driving  the  gases  through  the  chimney  itself. 
With  a  chimney  200  feet  high,  the  above  figures  would  be  doubled, 
and  there  would  be  a  difference  such  as  would  easily  occur,  say,  in 
Canada,  or  other  countries  subject  to  wide  variations  of  temperature, 
of  0*392  inches  water-gauge. 

TABLE  XV. 

TABLE  OF  PRESSURES  IN  INCHES  OF  WATER-GAUGE,  WITH  DIFFERENT 
TEMPERATURES  IN  CHIMNEY  AND  OUTSIDE  ATMOSPHERE. 


Tempera- 
ture in 
chimney. 

j.  eujptitttuic  ux  c-A-tciiiai  an. 

0° 

10° 

203 

30° 

40° 

50= 

60° 

70° 

80° 

90= 

100° 

200° 

0-453 

0-419 

0-384 

0-353 

0-321 

0-292 

0-263 

0-234 

0-209 

0-182 

0-157 

220° 

0-488 

0-453 

0-419 

0-388 

0-355 

0-326 

0-298 

0-269 

0-244 

0-217 

0-192 

240° 

0-520 

0-488 

0-451 

0-421 

0-388 

0-359 

0-330 

0-301 

0-276 

0-250 

0-225 

260° 

0-555  i  0-528 

0-484 

0-453 

0-420 

0-392 

0-363 

0-334 

0-309 

0-282 

0-257 

280° 

0-584 

0-549 

0-515 

0-482  I  0-451 

0-422 

0-394 

0-365 

0-340 

0-313 

0-288 

300° 

0-611 

0-576 

0-541 

0-511 

0-478 

0-449 

0-420 

0-392 

0-367 

0-340 

0-315 

320° 

0-637 

0-603 

0-568 

0-538 

0-505 

0-476 

0-447 

0-419 

0-394 

0-367 

0-342 

340° 

0-662 

0-638 

0-593 

6-563 

0-530 

0-501 

0-472 

0-443 

0-419 

0-392 

0-367 

360° 

0-687 

0-653 

0-618 

0-588 

0-555 

0-526 

0-497 

0-468 

0-444 

0-417 

0-392 

380° 

0-710 

0-676 

0-641 

0-611 

0-578 

0-549 

0-520 

0-492 

0-467 

0-440 

0-415 

400° 

0-732 

0-697 

0-662 

0-632 

0-598 

0-570 

0-541 

0-513 

0-488 

0-461 

0-436 

420° 

0-753 

0-718 

0-684 

0-653 

0-620 

0-591 

0-563 

0-534 

0-509 

0-482 

0-457 

440° 

0-774 

0-739 

0-705 

0-674 

0-641 

0-612 

0-584 

0-555 

0-530 

0-503 

0-478 

460° 

0-793 

0-758 

0-724 

0-694 

0-660    0-632 

0-603 

0-574 

0-549 

0-522 

0-497 

480° 

0-810 

0-776 

0-741 

0-710 

0-678  j  0-649 

0-620 

0-591 

0-566 

0-540 

0-515 

500° 

0-829 

0-791 

0-760 

0-730 

0-697    0-669 

0-639 

0-610 

0-586 

0-559 

0-534 

This  is  one  of  the  reasons  why  mechanical  draught  has  made  its 


BOILER   ACCESSORIES  135 

way.  It  will  be  seen  that  where  the  outside  atmosphere  is  subject 
to  changes  of  temperature  of  any  magnitude,  as  all  atmospheres  are, 
even  in  temperate  climates,  and  still  more  so  on  large  continental 
areas,  such  as  North  America,  etc.,  it  is  necessary  to  provide  a 
chimney  of  such  dimensions,  that  the  motive  column  is  always 
present,  even  in  the  very  hottest  weather,  and  this  means  that  the 
cost  of  the  chimney  is  very  much  greater  in  consequence,  and  that 
there  is  a  very  much  larger  waste  of  energy  in  the  hot  gases  passing 
up  the  chimney  than  would  otherwise  rule. 

The  height  of  the  chimney  is  also  ruled  indirectly  by  the  necessity 
of  providing  for  a  certain  definite  velocity  in  the  gases.  As  explained 
above,  a  certain  velocity  in  the  hot  gases  is  necessary  in  order  that 
the  air  from  which  they  are  formed  may  enter  the  furnace  in  proper 
proportion,  and  this  velocity  is  only  obtained  by  a  certain  definite 
motive  column  or  height  of  chimney.  Hence  the  chimney  is  obliged 
to  be  higher  in  some  cases  than  would  be  otherwise  necessary,  and 
than  would  apparently  be  necessary  from  an  examination  of  the 
height  and  area  of  the  chimney,  in  order  to  provide  for  this  velocity. 
The  final  solution  of  the  problem  is  somewhat  troublesome,  and  as 
usual  it  has  been  left  to  the  practical  engineer  to  work  out.  Mr. 
William  Kent,  the  author  of  the  "  Standard  Mechanical  Engineers' 
Pocket  Book  "  in  America,  has  produced  the  table  on  p.  136. 

The  table  is  based  upon  a  consumption  of  5  Ibs.  of  fuel  per  H.P. 
per  hour.  Modern  engines  work  with  considerably  less  than  that,  as 
explained  above,  but  the  differences  in  the  temperature  of  the  outside 
atmosphere,  and  also  changes  that  may  take  place  in  the  resistance 
offered  to  the  draught,  both  within  the  boiler  and  in  the  chimney, 
have  led  Mr.  Kent  to  provide  very  liberally  in  calculating  for  the 
horse-power. 

It  will  be  noted  that,  in  the  table,  the  diameters  of  different 
chimneys  are  given,  from  18  inches  up  to  12  feet,  these  being  for 
circular  chimneys,  and  the  equivalent  sizes  for  square  chimneys,  and, 
in  addition,  what  is  termed  the  effective  area  in  square  feet. 

By  effective  area  is  meant,  the  actual  space  within  the  chimney, 
operating  to  produce  the  required  velocity  of  the  gases.  As  already 
explained,  the  gases,  in  passing  through  the  chimney,  create  friction 
upon  the  sides  of  the  chimney,  and,  to  meet  this  friction,  the  actual 
area  through  which  the  gases  pass  is  taken  as  so  much  less  than  the 
total  area  of  the  chimney  itself. 

The  formula  upon  which  tfiis  is  calculated  is  as  follows  : — 

E  =  A  -  0-6  X  v'A 

The  height  of  chimneys  are  given  in  feet,  from  50  feet  up  to  300 
feet,  and  it  will  be  noted  that  the  chimneys  of  smaller  diameter  are 
given  smaller  heights,  the  heights  increasing  with  the  sectional  areas. 


136    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


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BOILER  ACCESSORIES  137 

It  will  be  noted  also  that  the  possible  H.P.  of  a  chimney  of  a  given 
sectional  area  increases  with  the  height,  a  chimney  of  18  inches 
diameter,  for  instance,  when  50  feet  high,  being  equal  to  the  service 
of  23  H.P. ;  at  60  feet  high  of  25  H.P.,  and  so  on.  The  reason  for 
this  is,  the  increased  height  furnishes  the  increased  motive  column, 
and  therefore  the  increased  velocity  of  the  gases,  and  the  increased 
passage  of  air  through  the  furnace,  and  therefore  increased  com- 
bustion. 

It  should  be  mentioned  that  what  is  called  the  intensity  of  the 
draught,  or  the  pressure  available  for  driving  the  air  and  gases  through 
the  furnace  in  the  chimney,  varies  as  the  square  root  of  the  height 
of  the  chimney,  and  this  is  because  the  height  of  the  chimney  varies 
with  the  velocity  of  the  gases. 


Construction  of  Boiler  Chimneys 

Boiler  chimneys  may  be  constructed  of  iron  or  steel,  or  of  brick- 
work, and  in  modern  plant  are  often  constructed  of  the  two  combined, 
the  chimney  being  built  of  steel,  lined  for  the  whole,  or  more  fre- 
quently a  portion,  of  its  length  with  brickwork.  For  small  boilers, 
such  as  those  of  portable  engines  and  small  boilers  in  positions  where 
the  smoke  is  not  of  consequence,  simple  iron  and  steel  cylinders, 
formed  from  iron  plates  bent  round  and  riveted  together,  and 
riveted  to  the  shell  of  the  boiler  where  the  flue  ends,  are  sufficient. 
For  larger  boiler  plants,  and  particularly  where  the  flue  gases  have  to 
be  delivered  at  a  height  where  they  will  not  be  a  nuisance,  up  till 
recently  the  common  plan  was  to  build  brick  chimneys,  which  were 
sometimes  circular  in  section,  sometimes  octagonal,  and  sometimes 
square.  The  circular  section  is  undoubtedly  the  best  form,  because 
the  whole  of  the  inside  of  the  chimney  is  employed  in  carrying  the 
gases ;  while  with  the  square  and  octagonal  forms  the  corners  often 
give  rise  to  eddies,  which  reduce  the  draught,  and  would  also  form 
pockets  for  the  passage  of  the  soot.  The  form,  however,  has  also  an 
important  bearing  upon  the  question  of  wind  pressure.  One  of  the 
problems  in  connection  with  the  building  of  chimneys  is  providing 
sufficient  strength  for  them  to  withstand  the  pressure  under  all  con- 
ditions, and  for  this  the  circular  chimney,  for  the  same  weight  of 
material,  exposes  only  half  the  surface  to  any  particular  wind  that 
may  be  blowing ;  or  put  it  in  another  way,  a  chimney  that  is  to  be  of 
a  given  height  and  a  given  sectional  area  may  be  half  the  weight  if  it 
is  circular  in  section  of  that  required  if  it  is  square,  and  the  pro- 
portion between  the  circular  and  octagonal  chimneys  is  as  4  to  5  for 
the  same  conditions. 

Another  very  important  point  in  connection  with  the  building  of 


138    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

chimneys — perhaps  the  most  important  point — is  the  foundation. 
The  foundation  of  the  chimney  must  be  of  a  certain  definite  depth 
and  width,  in  proportion  to  its  height  and  sectional  area. 

In  the  building  of  brick  chimneys  it  is  of  great  importance  that 
the  bricks  should  be  of  a  very  high  class,  and  that  very  much  greater 
care  should  be  taken  in  laying  the  bricks  than  with  ordinary  building. 
In  fact,  chimney  building  is  a  special  art  in  itself. 

Special  forms  of  bricks  have  been  designed  for  the  building  of 
chimneys,  and  amongst  them  may  be  noted  the  perforated  radial 
bricks  made  by  the  Alphons  Custodis  Construction  Company.  The 
chimney  is  designed  on  paper,  exactly  as  a  machine  is,  and  the 
bricks  for  the  chimney  are  also  designed  to  occupy  their  proper 
sectorship  of  the  cylinders  they  go  to  make  up.  It  is  claimed  for 
chimneys  built  with  these  bricks  that  they  stand  better,  and  that 
better  provision  is  made  for  expansion,  while  the  chimney  itself  is 
more  of  a  solid  structure  than  can  be  obtained  with  the  ordinary 
brick.  With  the  ordinary  brick,  it  will  be  understood,  the  angles 
formed  by  laying  the  bricks  together  to  form  a  cylinder  must  be 
filled  in  with  mortar ;  while  with  radially  designed  bricks  the  bricks 
themselves  form  the  cylinder,  the  only  office  of  the  mortar  being  to 
hold  the  bricks  together.  It  is  usual  to  build  an  outer  protective 
shell  with  ordinary  bricks,  though  it  is  claimed  that  this  is  not  neces- 
sary with  the  perforated  radial  bricks.  It  is  sometimes  arranged  to 
fix  water  tanks  about  halfway  up  the  chimney,  the  tank  taking  an 
annular  form,  the  lower  portion  being  inclined  to  the  vertical,  and 
being  supported  by  special  ledges  of  bricks,  a  cover  being  provided 
for  the  water  above.  This  arrangement  has  the  advantage  of  a  water 
tower  at  a  considerable  height  above  the  ground,  with  on]y  a  small 
expense  for  the  support  of  the  tank,  where  the  ordinary  water  tower 
would  be  a  somewhat  expensive  matter. 

Steel  chimneys  are  now  built  very  much  on  the  lines  of  steel 
boilers,  except  that,  as  they  have  not  so  much  pressure  to  withstand, 
it  has  not  been  found  necessary  to  take  such  great  care  in  the  forma- 
tion of  the  cylinders,  the  joints,  etc.  The  chimney  is  built  up  in 
sections,  each  section  being  made  of  sheets  from  8  to  10  feet 
in  length,  the  sheets  being  riveted  together  in  the  usual  way,  the 
rivet-holes  being  punched  instead  of  drilled.  Steel  chimneys  are 
made  either  to  be  supported  by  guys,  or  to  be  self-supporting.  Where 
there  is  a  difficulty  in  obtaining  a  good  foundation,  it  is  necessary 
to  support  the  chimneys  at  two  or  three  portions  of  their  height  by 
guys  or  stays  in  all  directions,  the  stays  consisting  of  wire  ropes, 
ending  in  rods  attached  to  anchors  in  the  ground.  Where  a  good 
foundation  is  obtainable,  the  chimney  is  made  self-supporting,  by 
giving  it  a  broad,  deep  foundation,  and  by  anchoring  its  base  by 
means  of  bolts. 


BOILER   ACCESSORIES  139 


Forced  Draught 

By  forced  draught  is  understood  the  passage  of  air  under  pressure 
through  the  boiler  furnace,  and  it  may  be  accomplished  in  two  ways. 
The  stoke-hold  may  be  closed,  and  the  air  that  is  to  pass  into  the 
furnace  may  be  forced  into  the  stoke-hold  under  a  certain  pressure, 
the  ashpits,  etc.,  being  left  in  the  ordinary  conditions.  The  stoke- 
hold may  be  left  under  ordinary  conditions,  and  the  ashpit  may  be 
closed  and  the  air  for  the  fires  delivered  under  pressure  to  each  ash- 
pit. The  closed  ashpit  system  is  necessarily  the  most  convenient  for 
the  great  majority  of  boilers  on  shore,  but  on  board  ship  the  closed 
stoke-hold  system,  or,  as  it  is  called  in  America,  the  closed  fire- 
room  system,  has  also  been  adopted,  particularly  in  the  case  of 
men-of-war.  The  objection  to  the  closed  stoke-hold  system  is  the 
fact  that  the  men  working  in  it  are  exposed  to  the  air  pressure,  and 
that  it  is  more  difficult  to  maintain  a  large  space,  such  as  the  stoke- 
hold, closed,  than  the  smaller  space  formed  by  the  ashpit.  One 
objection  to  the  closed  ashpit  system  is  the  number  of  connections 
that  have  to  be  made  from  the  pipe  bringing  the  air  to  the  different 
furnaces,  and  the  difficulty  of  delivering  the  air  uniformly  to  all  parts 
of  the  furnace.  There  is  a  tendency  to  blow  holes  in  the  fuel,  and  to 
cause  larger  heating  at  certain  grate-bars  than  at  others,  and  to  blow 
•  out  the  ashes,  etc.,  into  the  boiler-room.  In  the  case  of  the  closed 
stoke-hole  system,  providing  that  the  air  pressure  is  not  high,  the 
arrangement  is  good,  inasmuch  as  it  provides  ventilation  for  the 
stoke-hold  as  well  as  air  for  the  furnaces. 

Whichever  system  is  adopted,  whether  the  closed  ashpit  system 
or  the  closed  fire-room  system,  the  air  pressure  is  produced  by  means 
of  a  fan  placed  conveniently  to  the  fire-  or  boiler-room,  and  having  a 
duct  or  other  arrangement  leading  to  a  supply  of  fresh  air,  the  fan 
drawing  the  air  from  the  fresh  supply,  and  passing  it  either  directly 
into  the  stoke-hold  or  into  a  pipe  leading  to  the  different  ashpits. 

A  modification  of  the  forced -draught  system  provides  for  heating 
the  air  on  its  way  into  the  ashpit  or  boiler-room.  It  will  be  obvious 
that  the  system  is  not  applicable  to  the  case  of  the  closed  stoke-hold, 
inasmuch  as  the  men  would  be  subject  to  higher  air  temperatures 
than  they  are  at  present.  The  economy  of  the  system  is,  however, 
considerable. 

It  will  be  understood  that  with  forced  draught  the  fan  is  required 
to  produce  the  necessary  pressure  to  drive  the  air  into  the  furnace, 
through  the  fuel  and  the  hot  gases  which  are  formed,  through  the 
boiler  flues,  or  their  equivalent  in  water-tube  boilers,  and  also  to  force 
the  hot  gases  up  the  chimney.  A  portion  of  the  necessary  pressure 
will  be  provided,  wherever  there  is  a  chimney  of  any  appreciable 


140    STEAM   BOILERS,   ENGINES,  AND  TURBINES 

height,  by  the  motive  column  furnished  by  the  difference  between 
the  weight  of  the  hot  gases  in  the  chimney  and  the  equi- 
valent column  outside,  and  in  those  cases  the  fan  has  really 
only  to  provide  the  pressure  that  is  not  furnished  by  the 
chimney.  On  the  other  hand,  with  a  fan  forcing  air  into  the 
furnace,  it  is  not  necessary  to  provide  that  the  gases  ascending  the 
chimney  shall  have  any  appreciable  temperature  at  all  if  the  heat 
which  they  carry  can  be  economically  absorbed  before  they  reach  the 
chimney,  and  this  is  one  of  the  advantages  of  forced  draught  even 
where  a  chimney  is  already  in  existence.  It  will  be  remembered 
that  it  is  the  common  practice  to  deliver  the  hot  gases  to  the  chimney 
at  about  600°  F.,  because  this  is  about  the  temperature  up  to  which 
an  increased  pressure  is  obtained,  and  that  with  a  furnace  temperature 
of  2400°  F.,  this  means  that  25  per  cent,  of  the  heat  units  are  lost. 
When  forced  draught  is  applied,  the  temperature  of  the  hot  gases 
may  be  reduced  to  any  figure  the  engineer  pleases,  providing  that  he 


V 


flTMOSPMCRC 


FIG.  40.— Diagram  showing  the  course  of  the  Air  and  Hot  Gases,  with  Forced  Draught 

and  an  Economiser. 

can  get  them  away  comfortably  to  the  outer  atmosphere.  It  is  quite 
common  now  to  take  out  300°  of  temperature  from  the  hot  gases  by 
means  of  economisers,  and  to  deliver  them  to  the  chimney  at  300° 
only,  this  meaning  that  a  further  12 \  per  cent,  of  the  heat  units 
delivered  to  the  hot  gases  in  the  furnace  are  usefully  employed.  It 
appears  to  the  author,  subject  to  practical  considerations,  that  where 
forced  draught  is  employed  this  might  be  carried  very  much  further. 

Fig.  40  shows  diagram matically  the  course  of  the  air  and  hot 
gases,  in  a  Lancashire  or  Cornish  boiler,  with  forced  draught,  where 
an  economizer  is  used. 

In  addition  to  enabling  a  larger  percentage  of  the  heat  delivered 
to  the  hot  gases  to  be  usefully  employed,  forced  draught  enables  a 
higher  pressure  to  be  maintained  in  the  boiler  furnace,  and  hence 
enables  a  thicker  fire  to  be  employed,  the  fuel  lying  on  the  grate-bars 
in  larger  quantities,  and  therefore  a  larger  combustion  to  be  obtained 
from  a  given  grate  area ;  and  further,  the  quantity  of  air  supplied  to 


BOILER  ACCESSORIES  141 

the  furnace  to  be  considerably  reduced.  It  was  pointed  out  on  p.  130, 
that  the  common  practice  is  to  supply  double  the  quantity  of  air  to 
the  furnace  that  is  required  to  furnish  the  quantity  of  oxygen  neces- 
sary to  oxidize  the  whole  of  the  carbon  to  carbonic  acid.  This 
is  due  to  the  fact  that  with  chimney  draught,  which  is  limited, 
except  where  the  chimney  itself  has  been  built  on  very  liberal 
lines — and  even  then  sometimes  in  hot  weather — the  fuel  is  usually 
laid  on  the  furnace  bars  very  thinly,  so  that  the  air  may  easily  pass 
through,  and  the  proper  draught  be  maintained.  If  a  thick  fire  was 
maintained,  the  draught  would  be  checked,  and  the  combustion  would 
be  imperfect.  With  fan  draught,  as  practically  any  pressure  the 
engineer  chooses  can  be  maintained,  these  conditions  disappear.  The 
additional  pressure  necessary  to  drive  the  air  through  the  greater 
thickness  of  fuel  can  easily  be  provided,  and  as  then  a  larger  mass  of 
incandescent  fuel  is  produced,  combustion  is  very  much  better,  and 
the  quantity  of  air  necessary  in  order  to  provide  the  required  quantity 
of  oxygen  is  reduced  to  1^  times,  and  in  special  cases  to  1 J  times  the 
theoretical  quantity.  This  means  that  a  further  economy  is  obtained, 
because  the  6  or  9  Ibs.  of  air  per  pound  of  fuel  that  is  dispensed  with 
sets  free  the  heat  units  which  they  would  have  absorbed  for  raising 
the  temperature  of  the  fire  itself,  and  thence  increasing  the  radiation 
from  the  surface  of  the  fire,  which  has  a  very  important  effect  in  the 
heating  of  the  water  in  the  boiler ;  and,  in  addition,  the  hot  gases, 
starting  at  a  higher  temperature,  deliver  their  heat  more  readily  to  the 
metal-heating  surfaces  with  which  they  come  in  contact,  and  thence 
the  heat  is  more  readily  transmitted  to  the  water  on  the  other  side  of 
the  heating  surfaces,  and  the  whole  efficiency  of  the  boiler  is  raised. 

On  the  other  side  of  the  question  have  to  be  placed  the  charges 
for  driving  the  fan  to  produce  the  necessary  quantity  of  air,  and  the 
interest  upon  the  fan  and  engine  (or  motor),  ducts,  etc.,  but  against 
these  may  be  placed,  in  the  case  of  new  plant,  the  difference  in  the 
cost  of  the  chimney,  a  smaller  chimney  being  able  to  do  the  same 
work  with  forced  draught  as  the  large  one  did  with  chimney  draught. 


Induced  Draught 

By  induced  draught  is  meant,  sucking  or  exhausting  the  air 
through  the  furnaces,  flues,  etc.,  by  means  of  a  fan  placed  at  the 
back  of  the  boilers,  in  the  path  of  the  hot  gases  on  their  way  to 
the  chimney,  as  shown  diagrammatically  in  Fig.  41,  with  an 
economizer.  In  this  case  the  hot  gases  pass  through  the  fan,  and 
the  arrangement  of  the  fan  must  be  such  that  it  will  withstand  the 
high  temperatures  at  which  the  gases  are  delivered  to  it,  and  an 
arrangement  must  also  be  made  for  getting  rid  of  the  deposit  of 


142    STEAM   BOILERS,   ENGINES,  AND   TURBINES 

finely  divided  carbon,  or  soot,  that  is  deposited  from  the  hot  gases 
everywhere,  as  they  pass  from  the  boiler  to  the  atmosphere. 

One  important  point  must  be  noted  in  connection  with  induced 
draught,  as  distinguished  from  forced  or  pressure  draught,  viz.  the 
volume  of  gases  that  have  to  be  dealt  with.  With  forced  draught 
it  is  the  air  entering  the  furnace  which  is  at  the  ordinary  temperature 
of  the  atmosphere,  or  if  preheated,  at  whatever  temperature  it  may 
be  heated  to,  that  has  to  pass  through  the  fan.  With  induced 
draught  the  gases  have  to  pass  through  the  fan  at  the  temperature 
at  which  they  are  delivered  to  the  chimney,  and  their  volume  is  that 
due  to  that  temperature,  and  is  proportional  to  the  absolute  tempera- 
ture. At  600°  E.  their  volume  would  be  approximately  double  that 
at  60°,  the  average  temperature  of  air  in  this  country.  This  means 
that  the  power  employed  for  driving  the  fan  will  be  increased.  The 
power  will  not  be  doubled.  It  will  be  increased  approximately, 


FIG.  41. — Diagram  showing  the  course  of  Air  and  Hot  Gases  in  a  Lancashire  or" 
Cornish  Boiler,  with  induced  Draught  and  an  Economiser. 

with  proper  arrangements,  about  50  per  cent.  If  the  air  supplied  to 
the  furnace  by  a  pressure  fan  is  raised  to  300°,  the  difference  will 
only  be  about  half  that.  But,  again,  if  the  hot  gases  are  reduced  to 
300°  E.,  the  power  for  the  fan  is  reduced  in  proportion. 

Another  point  that  must  be  borne  in  mind  in  connection  with 
fans  employed  for  induced  draught,  is  that  of  the  bearings.  All 
parts  of  the  fan  will  necessarily  assume  a  temperature  closely 
approaching  that  of  the  gases  that  are  passing  through  it,  and  hence 
provision  must  be  made  for  lubricating  the  bearings  of  the  fan  at 
this  temperature.  This  is  not  a  difficult  matter,  but  it  is  one  of 
those  practical  points  that  must  be  attended  to. 

It  is  claimed  for  induced  draught,  that  it  is  a  more  convenient 
method  of  supplying  the  air  than  forced  draught,  because  it  does  not 
tend  to  blow  holes  in  the  fuel,  and  the  air  should  be  as  evenly  dis- 
tributed through  the  fuel  on  the  furnace  grate  as  with  chimney 
draught.  Induced  draught  is,  in  fact,  the  same  as  chimney  draught. 
Chimney  draught  is  really  induced  draught,  produced  by  a  chimney 
instead  of  by  a  fan. 


BOILER  ACCESSORIES  143 

It  is  claimed  also  that  the  trouble  which  sometimes  arises  from 
the  hot  gases  being  blown  outwards  through  the  furnace  doors,  or 
other  openings,  into  the  boiler-room  with  forced  draught,  is  absent 
with  induced  draught.  On  the  other  hand,  leakage  of  air,  which  is 
common  to  all  forms  of  draught,  is  all  inwards  with  induced  draught, 
and  with  chimney  draught ;  but  this  merely  means  that  a  larger 
quantity  of  air  is  present  in  the  chimney  gases,  robbing  them  of  a 
portion  of  the  heat  delivered  to  them,  and  thereby  reducing  the 
efficiency  of  the  boiler  as  a  whole.  It  will  be  evident  that  with 
increased  pressure,  the  leakage  will  increase,  and  in  proportion  to 
the  increased  pressure,  and  an  allowance  must  be  made  for  this  in 
considering  the  question  of  the  provision  of  draught. 

Leakage,  it  will  be  remembered,  takes  place  between  the  bricks 
employed  in  boiler  settings,  and  this  is  merely  a  matter  of  care  in 
setting,  of  selection  of  bricks,  and  of  care  in  supervision  after  the 
brickwork  has  been  set.  It  is  stated  that  with  some  boiler  settings, 
there  is  a  quite  appreciable  passage  of  leakage  air  through  the  joints 
and  the  brickwork,  into  the  side  flues  in  the  case  of  Lancashire  boilers, 
and  into  the  furnace  and  combustion  chambers  in  the  case  of  water- 
tube  boilers. 

With  induced  draught,  the  fan  is  usually  placed  in  a  separate 
passage,  leading  from  the  end  of  the  boiler  flue,  or  the  economizer 
chamber  to  the  chimney,  the  ordinary  passage  being  closed  by  a 
damper  when  the  fan  is  working,  and  allowed  to  remain  open  if 
anything  happens  to  the  fan,  and  the  chimney  draught  has  to  be 
relied  on. 


Induced  Draught  Combined  with  Heating  of  the 
Air  for  the  Furnace 

It  has  been  mentioned  on  p.  39,  in  connection  with  forced  draught, 
that  the  air  is  sometimes  heated  before  it  enters  the  furnace.  This 
plan  is  also  adopted  in  connection  with  induced  draught.  In  par- 
ticular, Messrs.  John  Brown  &  Co.,  of  Sheffield,  have  worked  out. the 
Ellis  and  Eaves  system  of  induced  draught  with  air  heating,  principally 
for  use  on  board  ship,  but  they  have  also  adapted  it  to  land  boilers. 
The  arrangement  for  use  on  board  ship  is  shown  in  section  in  Figs. 
42  and  43,  one  of  which  is  a  cross  section,  and  the  other  a  longitudinal 
section,  through  a  marine  boiler  of  the  ordinary  multitubular  type. 
The  air  heating  arrangement  is  fixed  in  the  front  of  the  boiler,  where, 
it  will  be  remembered,  the  uptake  for  the  hot  gases  leading  to  the 
funnel  is  fixed.  The  air-heating  arrangement  consists  of  a  number 
of  tubes  fixed  vertically,  as  shown,  in  the  uptake,  so  that  the  hot 
gases  passing  to  the  funnel  are  obliged  to  pass  through  them,  and 


H4    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


BOILER   ACCESSORIES  145 

the  air  to  be  heated  passes  around  the  tubes,  and  is  then  conducted 
to  the  stoke-hold.     The  course  of  the  air  and  of  the  flue  gases,  is 
shown  by  the  arrows  in  the  longitudinal  section.     The  fan  is  fixed 
above  the  boiler,  and  is  driven  by  its  own  engine  fixed  behind,  with 
a  long  shaft,  the  bearings  of  the  fan  being  water  cooled.     For  land 
boilers  a  somewhat  similar  arrangement  is  made.     The  apparatus  has 
also  been  fixed  to  Babcock  and  Wilcox  boilers.     As  in  the  marine 
boiler,  a  number  of  tubes  are  placed  vertically  above  the  boiler,  and 
in  the  path  of  the  hot  gases  on  their  way  to  the  chimney,  and  the 
air  to  be  heated  passes  over  the  outside  of  the  tubes,  and  is  con- 
ducted thence  by  means  of  pipes  provided  for  the  purpose,  to  the 
ashpit.     As  will  be   recognized,  this  arrangement  is  an  adaptation 
to  air  heating  of  the  principle  that  is  employed  for  heating  feed 
water  by  means  of   the  hot  gases  and  exhaust   steam.     It  will  bo 
understood,  of  course,  that  the  chimney  will  not  produce  as  great 
an  intensity  of  draught,  that   is   to  say,    as   high   a   water-gauge, 
when  any  air  or  water  heating  apparatus  is  interposed  between  the 
boiler  and   the  chimney,  or  when  any  further  quantity  of   heat  is 
taken  out  of  the  gases,  above  that  taken  out  in  the  boiler  itself ;  but, 
as  already  explained,  where  there  is  a  fan  draught,  this  does  not 
matter,  and  the  loss  of  water-gauge  is  more  than  compensated  for 
by  the  economy  in  coal  produced  by  heating  the  air.     In  the  Ellis 
and  Eaves  system,  the  air  is  heated  to  about  300°  F.,  and  it  is  claimed 
that  the  air  heating  and  fan  combined,  produce  an  economy  of  from 
10  to  15  per  cent,  in  the  coal  consumed  in  the  furnace.     That  is 
to  say,  the  coal  saved  by  heating  the  air,  less  the  coal  required  to  be 
burned  to  make  the  steam  for  driving  the  fan  engine,  amounts  to 
from  10  to  15  per  cent,  of  the  coal  consumed  with  chimney  draught. 


Forms  of  Fans  Employed  for  Mechanical 
Draught 

There  are  two  kinds  of  fans  made,  known  as  the  propeller  and 
the  centrifugal  fan.  Only  the  centrifugal  fan  is  of  any  use  for 
furnishing  draught  to  boilers.  The  propeller  fan  is  merely  a  screw, 
similar  in  construction,  though  smaller,  to  the  screw  of  a  steam  ship, 
and  it  screws  the  air  from  one  side  of  it  to  the  other,  just  as  the 
water  is  screwed  from  one  side  of  the  propeller  to  the  other ;  so  that, 
if  a  fan  of  the  kind  is  placed  in  a  partition,  such  as  the  outer  wall  of 
a  room,  when  revolved,  it  will  cause  a  passage  of  the  air  either  from 
outside  into  the  room,  or  from  the  room  to  the  outside,  according  to 
the  direction  in  which  it  is  turned. 

Its  blades,  or  areas,  are  really  sections  of  a  screw.  This  form  of 
fan  can  only  be  employed  where  the  pressure  required  is  very  small 

L 


146    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

indeed.  It  is  used  for  ventilating  buildings,  but  even  there  only 
where  the  system  of  ducts  is  so  arranged  that  the  total  resistance 
offered  to  the  passage  of  the  air  requires  the  expenditure  of  only 
a  small  fraction  of  an  inch  water-gauge  to  overcome  it.  At  the 
Birmingham  General  Hospital,  for  instance,  where  2,000,000  cubic 
feet  of  air  pass  through  the  building  per  minute,  the  pressure  is  only 
^j-  inch  water-gauge,  and  a  number  of  large  fans  of  the  propeller 
type  are  able  to  deal  with  it. 

In  the  centrifugal  fan  the  air  is  carried  outwards  from  the  centre 
to  the  periphery  of  the  fan  by  centrifugal  action.  Centrifugal  fans 
vary  very  much  in  construction,  but  all  are  on  certain  main  lines. 
In  all  of  them  there  is  a  central  circular  aperture,  forming  the  inlet 
for  the  air,  and  a  number  of  blades,  usually  held  between  two  discs, 
and  a  number  of  openings  at  the  circumference.  As  the  fan  is 
revolved,  the  air  lying  between  the  blades  is  propelled  outwards  by 
centrifugal  force,  and  this  creates  a  difference  of  pressure  between 
the  inlet  aperture  and  each  of  the  outlets.  The  air  from  the  outside 
atmosphere,  or  the  atmosphere  to  which  the  inlet  is  connected,  rushes 
into  the  space  where  the  lowered  pressure  rules,  the  result  being  a 
continual  passage  of  air  through  the  fan.  The  outlets  to  the  fan  are 
arranged  to  pass  in  front  of  a  chimney,  or  duct  of  some  kind,  at  a 
certain  period  of  the  revolution,  and  to  discharge  their  air  into  it. 
In  some  forms  of  fan  the  chimney  or  duct  is  given  what  is  called  an 
evase  form,  the  object  being  to  reduce  the  velocity  of  the  air  as  it 
leaves  the  fan. 

Strictly  speaking,  the  fans  for  forced  draught,  and  for  induced 
draught,  should  be  differently  constructed,  but  in  practice  any  fan 
may  be  employed  for  either,  providing  that  it  will  furnish  the 
necessary  pressure,  and  accommodate  the  gases,  or  air,  that  has  to 
pass  through  it.  For  forced  draught  the  inlet  is  open  to  the  outside 
atmosphere,  the  outlet  or  duct  being  connected  either  to  the  stoke- 
hold, or  to  the  duct  leading  to  the  ashpits.  For  induced  draught 
the  inlet  is  connected  to  a  duct  leading  to  the  boiler  flues,  and  the 
outlet  to  a  duct  leading  to  the  chimney. 


Sizes  of  Fan  required 

As  with  chimneys,  so  with  fans,  there  are  two  requirements. 
The  fan  must  be  wide  enough,  in  a  direction  measured  at  right  angles 
to  the  radius,  to  accommodate  the  whole  of  the  air  or  gases  without 
throttling  them.  It  must  also  furnish  a  sufficient  pressure  to 
overcome  the  resistance  of  the  furnace,  boiler  flues,  and  chimney. 

The  volume  of  air  or  gases  any  fan  will  accommodate,  depends 
directly  on  its  width.  The  pressure  the  fan  will  create  depends 


BOILER   ACCESSORIES  147 

directly  upon  the  square  of  the  speed  at  which  its  blade  tips  are 
travelling,  and  the  power  absorbed  in  moving  the  air  depends 
directly  upon  the  cube  of  the  speed  of  the  fan.  The  power  required  to 
move  a  given  quantity  of  air,  is  given  by  the  formula  W  =  p  X  a  X  v, 
where  W  is  the  work  performed  in  moving  the  air,  p  is  the  pressure 
under  which  it  is  moved,  a  is  the  area  in  square  feet  over  which  it  is 
moved,  and  v  is  the  velocity  of  the  air  in  feet  per  second.  The 
formula  may  be  reduced  to  the  following  :  — 


in  which  W,  as  before,  is  the  work  performed  in  moving  the  air  or 
gases,  d  is  the  density  compared  with  air  at  standard  pressure, 
a  is  the  area  in  square  feet  over  which  it  is  moved,  and  v  is  the 
velocity. 

From  this  it  will  be  seen  that  the  power  varies  as  the  cube  of 
the  velocity,  and  as  the  velocity  of  the  air  depends  directly  upon  the 
velocity  of  the  fan,  the  power  required  depends  directly  upon  the  cube 
of  the  speed  of  the  fan. 

The  power  required  to  move  any  given  quantity  of  air,  with  any 
given  water,  is  given  by  the  formula. 

The  power  required  to  be  delivered  to  the  fan  shaft,  in  order  to 
provide  the  given  velocity  of  air  with  the  given  pressure,  is  found  by 
equating  the  power  found  from  the  last  formula,  with  the  efficiency 
of  the  fan.  The  efficiency  of  the  fan  may  be  taken  as  40  to  50  per 
cent. 

Draught  by  means  of  Steam  Jets 

This  method  is  really  a  form  of  induced  draught,  and  it  operates 
on  the  same  principle  as  the  injector.  It  has  various  forms,  but  in 
all  of  them  a  tube  is  inserted  in  the  side  of  the  boiler,  under  the 
grate  bars,  and  a  steam  pipe,  ending  in  a  nozzle,  is  fixed  centrally  in 
this  tube,  the  steam  passing  from  it  under  and  up  through  the  fire 
bars,  and  by  creating  a  difference  of  pressure  between  the  inner  end 
of  the  tube  and  the  outer  atmosphere,  drawing  the  air  after  it,  the 
air  passing  up  between  the  fire  bars,  through  the  fuel  and  so  on. 
Fig.  44  shows  the  form  of  Messrs.  Meldrum's  furnace  in  which 
draught  is  induced  by  steam  jets,  and  also  the  form  of  the  jet  and  air 
inlet.  It  is  arranged  that.  the  steam  jet,  which  is  taken  from  the* 
boiler,  is  superheated,  by  passing  through  a  pipe  above  the  furnace 
before  entering  the  nozzle.  It  is  claimed  that  the  steam  jet  keeps 
the  furnace  bars  cool  by  condensing  on  them  and  being  re-evaporated 
afterwards. 

There  is  the  usual  controversy  between  advocates  of  steam-jet 


148     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

draught,  and  fan  draught ;  but,  as  usual,  all  of  the  forms  are  applicable 
to  certain  cases.     The  steam-jet  method  has  the  advantage  of  lower 


FIG.  44. — Longitudinal  Section  of  a  Lancashire  Boiler,  fitted  with  Meldrum's  Fire 
Bars  and  their  Steam  Jet.  The  Steam  Jet  is  fixed  inside  the  Trumpet  shown  in 
the  Ash-pit,  the  Steam  being  taken  from  the  Boiler  and  superheated  by  being 
passed  through  the  Tube  shown,  in  the  front  of  the  Furnace. 

first  cost,  and  the  absence  of  moving  parts.     It  is  also  easily  applied 
to  existing  boilers. 

Messrs.  Grainger  make  an  adjustable  nozzle  for  steam -jet  draught. 


Boiler  Dampers 

Dampers  are  fitted  to  all  boiler  flues,  to  enable  a  certain  control 
to  be  obtained  over  the  draught.  Even  where  forced,  or  induced 
draught  is  employed,  dampers  are  always  fixed.  They  are  virtually 
gas  valves,  controlling  the  passage  of  the  hot  gases,  and  thence  the 
air  entering  the  boiler  furnaces,  and  consist  of  doors  arranged  to 
completely  fill  up  the  flues  in  which  they  are  placed.  Their  position 
is  controlled  by  a  system  of  levers  and  chains  from  the  front  of  the 
boiler,  operated  by  the  stoker.  Closing  the  dampers  prevents  all 
passage  of  the  hot  gases,  and  nearly  prevents  the  admission  of  air  to 
the  furnace.  If  there  were  no  air  leakage  it  would  do  so.  Partially 


BOILER  ACCESSORIES  149 

closing  the  damper  throttles  the  supply  of  air,  just  as  partially  closing 
a  steam  valve  throttles  the  passage  of  steam. 


Automatic  Damper  Regulators 

The  dampers  are  sometimes  controlled  automatically  by  the  pressure 
of  the  steam,  the  damper  being  partially  closed  when  the  steam 
pressure  rises,  and  opened  when  it  falls.  One  apparatus  designed  for 
this  is  the  Patterson  hydraulic  damper  regulator,  made  at  Baltimore 
in  America.  The  apparatus  is  designed  to  work  the  damper  by  a 
hydraulic  motor,  which  moves  a  chain  up  and  down,  the  chain  passing 
over  pulleys  which  move  the  damper  up  and  down.  The  hydraulic 
motor  is  operated  by  a  balance  controlled  by  a  small  steam  cylinder, 
to  which  the  pressure  of  the  boiler  is  admitted,  a  steelyard  enabling 
the  time  at  which  the  apparatus  comes  into  operation  to  be  varied  at 
will.  As  the  steam  pressure  rises  or  falls,  the  admission  of  the  water 
under  pressure  to  the  hydraulic  cylinder  is  controlled,  and  the  damper 
is  moved  up  and  down. 


The  Lagonda  Damper  Regulator 

This  is  another  apparatus  intended  to  automatically  control  the 
motion  of  the  damper  in  accordance  with  variations  of  the  steam 
pressure.  It  consists  of  a  steelyard,  on  which  a  balance  weight  is 
suspended,  the  position  of  which  can  be  varied,  according  to  the  will 
of  the  engineer,  the  steelyard  .being  moved  up,  against  the  pull  of 
the  balance  weight,  by  the  pressure  of  water  upon  a  diaphragm 
enclosed  in  a  cylindrical  space.  The  entrance  of  water  into  the 
cylinder  containing  the  diaphragm  is  controlled  by  a  second  lever, 
with  a  balance  weight,  opposing  a  second  cylinder  with  a  diaphragm. 
The  pipe  leading  to  the  first  diaphragm  and  the  cylinder  containing 
the  second  diaphragm  are  full  of  water  under  ordinary  conditions, 
and  the  pressure  of  the  water  maintains  the  damper  in  the  position 
in  which  the  engineer  wishes  it  to  remain.  If  the  steam  pressure 
rises,  the  pressure  inside  the  first  diaphragm  is  increased,  and  the 
lever  to  which  it  is  attached,  moves  in  the  direction  for  closing  the 
damper.  On  the  other  hand,  if  the  steam  pressure  falls,  the  lowered 
pressure  is  made  to  allow  a  portion  of  the  water  to  run  out,  to  lower 
the  pressure  under  the  diaphragm  controlling  the  damper  lever,  this 
causing  motion  in  the  direction  for  opening  the  damper.  There  is 
a  valve  in  connection  with  the  second  diaphragm,  which  controls  the 
admission  of  water  and  steam  in  accordance  with  the  requirements 
of  the  service. 


150     STEAM   BOILERS,   ENGINES,   AND    TURBINES 


Messrs.   Eraser  &   Chalmers   also   make   an   automatic   damper 
regulator,  the  details  of  which  are  shown  in  Fig.  45.     They  are  very 

similar   to    those  described 

(Locke's  Patent.)  above,  the  hydraulic  cylin- 

der on  the  right  controlling 
the  apparatus.  Water  at 
a  pressure  of  20  Ibs.  per 
square  inch  is  required. 


Boiler  Cleaners 

The  deposit  of  foreign 
matter  and  the  formation 
of  scale  upon  the  water 
surface  of  boilers,  has  been 
referred  to,  and  the  different 
devices  explained  for  pre- 
venting a  deposit.  In  spite 
of  all  that  has  been  done 
in  that  direction,  sometimes 
owing  to  imperfect  attend- 
ance, and  from  other  causes, 
it  is  found  that  scale  is  still 
formed,  and  in  the  case  of 
the  tubes  of  water -tube 
boilers,  the  matter  may  be- 
come very  serious,  as  the 
bore  of  the  tubes  is  con- 
siderably reduced,  and  in 
addition,  as  explained  so 
frequently,  the  resistance 


FIG.  45. — Automatic  Hydraulic  Damper  Eegu- 
lator,  made  by  Messrs.  Fraser  and  Chalmers. 


The  Hydraulic  Cylinder  is  shown  on  the      offered    to    the    passage    of 

virrli4:          "Rnnmla  4-.i  /-\>-»    10    /~\fts\si4-s\rl    "U-rr  14-     4-»-»     ^/^-v->  _    *T  O 


right.  Regulation  is  effected  by  it,  in  con- 
nection with  the  Steel  Yard  shown  in  the 
centre  and  the  Steam  Cylinder  on  the  left. 


nection  with  the  Steel  Yard  shown  in  the       heat  from  the  hot  gases  to 


the   water  is    considerably 
increased.      To   meet   this, 

several  apparatus  have  been  designed  for  the  purpose  of  removing 
the  scale. 

The  Weinland  mechanical  boiler-tube  cleaner,  designed  specially 
for  water-tube  boilers,  has  a  head  shaped  very  much  like  a  screw 
point,  which  is  intended  to  bore  its  way  into  the  scale,  and  behind 
the  head  are  a  number  of  conical  steel  cutters,  gradually  increasing 
in  size,  and  increasing  the  bore,  as  the  machine  moves  forward. 
Behind  the  conical  cutters  are  two  sets  of  cylindrical  cutters,  carried 
on  pins,  and  revolving  freely.  The  action  of  the  apparatus  is  very 


BOILER  ACCESSORIES  151 

much  like  that  of  a  milling  machine,  after  the  screw  head  has  bored 
its  way  in,  the  cutters  being  practically  milling  tools,  arranged  to 
cut  the  scale  instead  of  metal.  The  apparatus  is  held  at  the  end  of 
a  rod,  long  enough  to  allow  it  to  go  right  through  the  boiler  tube  to 
be  cleaned,  and  is  revolved  by  a  strap,  from  any  convenient  source 
of  power,  or  by  an  electric  motor.  For  curved  tubes,  such  as  those 
of  the  Stirling  and  other  boilers,  a  special  arrangement  is  made, 
enabling  the  cleaner  to  go  round  the  curves.  The  apparatus  is 
employed  for  cleaning  out  filter  tubes,  economizer  tubes,  feed-water 
heater  tubes,  and  in  fact  anywhere  that  deposit  may  form. 


Turbine  Boiler-Tube  Cleaners 

The  self-acting  turbine  driven  pipe  cleaner  is  an  apparatus  well 
known  to  water-works  engineers,  and  very  much  employed  by  them 
for  cleaning  off  the  scale  that  forms  on  the  inside  of  water  pipes.  It 
consists  of  a  small  turbine,  of  sufficient  size  to  drive  the  cleaning 
apparatus,  carried  on  an  axle,  to  which  are  also  attached  usually  three 
or  more  cutting  tools,  revolving  on  their  own  axes.  In  cleaning  the 
tubes  of  water  works,  the  force  of  the  water  current  is  made  to  drive 
the  apparatus  by  the  aid  of  the  turbine,  and  the  same  arrangement  is 
made  use  of  for  driving  turbine  boiler-tube  cleaners,  water  being 
supplied  from  any  convenient  source  for  the  purpose.  The  Weinland 
turbine  boiler-tube  cleaner,  made  by  the  Lagonda  Manufacturing 
Company,  is  on  these  lines. 

A  steam  jet  is  a  very  favourite  device  for  cleaning  the  tubes  of 
water-tube  boilers,  the  steam  being  delivered  at  the  entrance  of  each 
tube  into  its  header  by  means  of  a  flexible  metallic  tube  and  a 
nozzle.  The  pressure  of  steam  breaks  up  the  deposit,  and  the  injector 
action  assists. 

Boiler  Fittings 

The  fittings  required  for  a  boiler  consist  of  a  stop  valve,  a  safety 
valve,  feed  pipe,  and  check  valve,  scum  pipe  and  cock,  and,  in 
addition,  gauge  cocks  and  steam-  and  water-gauges.  Gauge  cocks 
are  not  so  often  now  fitted  as  in  the  earlier  days  of  steam.  Where 
they  are  used  there  are  three — one  in  the  water  space,  one  in  the 
steam  space,  and  one  on  the  level  where  water  and  steam  should 
come  together.  When  the  lower  one  is  turned  on,  water  issues ; 
when  the  upper  one  is  opened,  steam  issues ;  and  when  the  middle 
one,  water  and  steam.  Gauge  cocks  are  only  intended  to  be  used 
when  the  proper  gauges  are  not  working.  The  proper  water-gauge 
has  two  cocks,  one  fixed  in  the  water  space  and  the  other  in  the 


152     STEAM   BOILERS,  ENGINES,   AND   TURBINES 

steam  space,  with  a  substantial  glass  tube  connecting  them,  the  tube 
being  protected  by  brass  fittings,  in  modern  practice.  When  the 
two  cocks  are  open,  the  position  of  the  water  in  the  gauge  corresponds 
with  that  in  the  boiler.  The  water-gauge  is  drained  by  a  small  pipe. 
In  addition,  a  steam-gauge  is  always  fixed  on  the  front  of  the 
boiler.  It  consists  of  a  shallow  cylindrical  case,  with  a  glass  front, 
and  a  dial  behind  the  glass,  over  which  a  needle  pointer  sweeps. 
The  pointer  is  pivoted  at  its  centre  in  the  usual  way,  and  is  moved 
by  a  toothed  wheel,  gearing  into  a  rack,  forming  a  sector  of  a  circle, 
and  attached  to  the  end  of  a  small  metal  tube,  the  other  end  of 
which  is  connected  by  a  pipe  to  the  steam  space,  whose  pressure  is 
to  be  gauged.  The  motion  of  the  pointer  is  resisted  by  a  spiral 
spring,  coiled  round  the  pivot  upon  which  the  pointer  moves.  The 


FIG.  46. — A  complete  Steam  Gauge,  with        FIG.  47. — The  Steam  Gauge  shown  in 
Dial  and  Needle.  Fig.  46,  with  Dial  removed,  showing 

the  Tube  upon  which  the  Steam 
acts  and  the  Gearing  giving  motion 
to  the  Pointer. 

heat  delivered  to  the  pipe  by  the  steam  causes  it  to  expand,  and  its 
free  end  turns  the  pointer  round,  in  opposition  to  the  spring  men- 
tioned, the  dial  being  graduated  in  accordance.  It  is  usual  in  steam 
boilers  to  mark  the  positions  on  the  dial  of  safe-working  steam 
pressure.  Figs.  46  and  47  show  one  form  of  steam-gauge,  and  Fig. 
48  shows  a  Lancashire  boiler  with  all  fittings. 

Safety  Valves 

The  safety  valve  has  become  almost  a  proverb.  It  is  an  absolute 
necessity  in  the  case  of  all  steam  work,  and  by  Board  of  Trade  regu- 
lations is  obliged  to  be  fixed  upon  all  boilers.  The  object  of  the 


BOILER  ACCESSORIES 


safety  valve  is  to  relieve 
the  boiler,  should  the 
pressure  within  it  rise 
above  a  certain  figure. 
All  boilers,  as  explained, 
are  constructed  of  mate- 
rials that  are  calculated  to 
resist  strains  from  within, 
of  several  times  the  maxi- 
mum they  should  meet 
with  under  ordinary  con- 
ditions. But  there  are 
cases,  by  no  means  so 
common  now  as  in  days 
gone  by,  where  steam  ac- 
cumulates, it  not  being 
used  by  the  engines,  and 
the  fires  remaining  burn- 
ing, the  pressure  of  the 
steam  continuing  to  in- 
crease, in  which,  unless 
some  relief  were  made, 
the  boiler  would  burst, 
and  steam  and  boiling 
water  would  be  forced 
out  into  the  boiler-room, 
scalding,  and  probably 
killing,  those  present.  As 
it  is,  even,  when  boilers 
are  allowed  to  become 
weak,  their  shells  being 
eaten  away  gradually  in 
places,  and  nothing  being 
known  of  the  fact,  the 
pressure  of  steam  the 
boiler  is  allowed  to  fur- 
nish not  being  decreased, 
a  day  comes  when  a  little 
increase  of  pressure  breaks 
through  one  of  the  weak 
spots,  and  disaster  is  the 
result. 

No  safety  valve  can 
p'ossibly  provide  for  care- 
lessness of  the  kind  last 


154    STEAM   BOILERS,  ENGINES,  AND   TURBINES 


mentioned,  but  it  can  and  does  provide  for  accidental  accumula- 
tion of  steam,  and  therefore  the  increase  of  pressure  beyond  a  safe 
limit.  Safety  valves  are  arranged  to  open,  and  to  allow  the  steam 
to  escape,  if  the  pressure  rises  above  a  certain  fixed  point,  for  which 
the  valve  is  set. 

There  are  three  forms  of  safety  valves  on  the  market,  that  may 
be  described  as  lever  valves,  spring  valves,  and  dead- weight  valves. 

The  earliest  form  of  the  safety  valve  was  the  lever  valve.  The  valve 
itself  may  be  of  any  one  of  the  well-known  types  of  valves,  the  moving 
portion  of  which  is  controlled  by  a  vertical  rod,  attached  to  a  lever 

of  the  second  order,  the  lever 
having  a  movable  weight  upon 
its  arm.  The  position  of  the 
weight  rules  the  pressure  of 
steam  at  which  the  valve  will 
open,  and  the  weight  itself  is 
proportional  to  the  difference 
between  the  arms  of  the  lever. 
Thus,  if  the  safety  valve  has 
an  area  of  2  square  inches, 
and  the  rod  controlling  its 
motion  is  2  inches  from  the 
fulcrum,  while  the  weight  is 
12  inches  from  the  fulcrum, 
if  the  valve  is  required  to  open 
with,  say,  a  pressure  of  80  Ibs. 
per  square  inch,  the  weight 


must  equal 


9 


=  23-3  Ibs., 


say  24  Ibs.,  and  the  pressure 
at  which  the  valve  opens  can 
be  increased  or  decreased  by 
FIG.  49.— Section  of  Eaves'  Dead-weight  Safety   sliding  the  weight  along  the 

"\7r»lTT/-»  ^  O  O 


Valve. 


rod. 


In  spring  valves,  a  spiral 

spring  takes  the  place  of  the  lever  and  weight  described  in  the  last 
form.  The  tension  of  the  spring  can  be  regulated  by  a  nut  above  it 
in  the  usual  way,  and  the  pressure  of  steam  at  which  the  valve  opens 
is  regulated  by  the  position  of  the  nut. 

In  the  dead-weight  valve,  which  is  gradually  coming  into  general 
use,  the  vertical  member  controlling  the  opening  of  the  valve  has  a 
horizontal  collar  over  which  are  slipped  rings,  forming  the  weight 
required.  Steam  passes  up  through  the  central  opening,  and  when 
the  pressure  exceeds  that  for  which  the  valve  is  set,  it  lifts  the 
whole  thing  bodily. 


BOILER  ACCESSORIES  155 

In  Eaves'  dead-weight  safety  valve,  which  is  made  by  Messrs. 
John  Brown  and  Co.,  and  which  is  shown  in  Fig.  49,  the  action  is 
twofold.  The  valve  itself,  it  will  be  seen,  is  a  spherical  ball,  and 
when  the  pressure  in  the  boiler  exceeds  that  for  which  the  valve  is 
weighted,  the  outside  portion  lifts,  and  allows  the  steam  to  escape  by 
the  side  passages.  If  the  steam  does  not  immediately  go  down,  a 
further  action  takes  place,  the  central  portion  lifting,  and  allowing 
a  further  escape  of  steam. 


Atmospheric  Relief  Valve 

The  atmospheric  relief  valve  is  not  much  heard  of  now,  but  it 
was  of  considerable  importance  in  the  early  days  of  steam  work.  If 
a  boiler  was  allowed  to  become  cold,  its  furnaces  to  go  out,  and  its 
steam  to  condense,  it  happened  in  the  early  days  of  steam  that  at 
times  the  pressure  of  the  atmosphere  was  greater  than  the  pressure 
inside  the  boiler,  the  result  being  that  portions  of  the  boiler  were 
forced  inwards.  To  meet  this  the  early  boilers  were  fitted  with 
atmospheric  valves,  which  opened  inwards,  in  the  same  manner  as 
the  safety  valve  opens  outwards,  admitting  air,  and  equalizing  the 
pressure  within  and  without  the  boiler.  The  increased  pressures 
employed,  and  the  consequently  increased  tensile  strength  of  the 
materials  of  which  boilers  are  composed  has  rendered  the  atmospheric 
valve  unnecessary. 


High  and  Low  Water  Safety  Apparatus 

In  addition  to  the  ordinary  safety  valve,  relieving  the  pressure 
on  the  boiler  when  it  exceeds  a  certain  figure,  the  modern  boiler  is 
further  protected  by  apparatus  designed,  in  some  cases,  to  sound  an 
alarm  whistle  if  the  level  of  the  water  is  too  high  or  too  low  in  the 
boiler,  and  in  other  cases  to  open  a  safety  valve,  sometimes  arranged 
specially  for  the  purpose,  and  sometimes  forming  the  ordinary  safety 
valve  of  the  boiler.  The  arrangement  is  shown  in  Fig.  50,  from 
which  it  will  be  seen  that  there  are  two  floats,  suspended  from  opposite 
arms  of  a  lever— one  the  low- water  float,  and  the  other  the  high- water 
float.  The  high-water  float  is  always  out  of  the  water,  except  when 
it  rises  above  a  certain  depth.  The  low- water  float  is  always  in  the 
water,  and  its  weight  is  always  taken  by  the  water,  except  when  the 
water  falls  to  a  certain  depth.  In  that  case  the  low- water  float 
commences  to  bring  weight  upon  its  end  of  the  lever,  and  if  the 
water  continues  to  fall,  it  either  blows  the  whistle,  or  opens  the 
valve,  allowing  steam  to  escape.  It  will  be  understood  that  there 


156    STEAM   BOILERS,   ENGINES,   AND  TURBINES 

is  great  danger  in  allowing  a  boiler  to  run  dry,  while   it  is  still 
making  steam. 


LOAT.  ~ 


|p  TILT      F 


FIG.  50. — Section  of  High-steam  Pressure,  and  Low- Water  Safety  Valve  fitted  to 
Lancashire  Boiler,  as  made  by  Messrs.  Alley  and  McLellan. 


Combined  Stop  and  Safety  Valve 

For  economy  it  is  sometimes  arranged  to  combine  the  safety  valve 
and  the  stop  valve  in  one.  It  is  opened  by  hand  in  the  usual  way, 
and  opens  with  an  excess  pressure  of  steam. 

Stop  valves  are  described  on  p.  254.  The  stop  valves  used  for 
disconnecting  a  boiler  from  service  is  of  the  same  fonn;  etc.,  as  that 
used  for  connecting  and  disconnecting  an  engine. 


Heating  the  Feed  Water  for  the  Boilers 

It  has  been  pointed  out  in  the  previous  chapter  that  it  is 
advantageous  to  heat  the  feed  water  entering  the  boiler  to  as  nearly 
the  temperature  of  the  water  from  which  steam  is  being  produced  as 
possible,  because  of  the  effect  upon  the  circulation.  It  has  also  been 
pointed  out  that  there  is  a  considerable  waste  in  the  hot  gases  when 
delivered  to  the  chimney  at  600°  F.,  and  that  while  600°  K,  or  there- 
abouts, is  the  limit  at  which  increased  draught  is  obtained,  there  is 


BOILER  ACCESSORIES 


v^ii-  :* •  »*:~.J!-- ,    ISF \ ' Y^-  -W."'*  •  Xy  v   _    •  .      v      T \  .i*-,",.  -K  Jy^v-    1'^-^ 


.^^^s:^^p^^fe^ 

•'V.Sfi\l»cir.«j^i-:« •>'•.">>!»"** » '.  ?T..  '  •<  >j''r\"T^ 


'^    -; 


FIG.  51. — Elevation  of  Green's  Economizer,  with  parti  of  the  Brickwork  removed,  to 

show  the  Tubes. 


FIG.  52. — Sectional  Plan  of  Green's  Economizer. 


158    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


very  little  difference  between  the  draught  obtained  at  300°  F.,  and 
that  at  600°  F.  In  connection  with  this,  however,  the  fact  of  the 
variation  in  the  temperature  of  the  outside  air,  and  its  effect  upon 
the  intensity  of  the  draught,  with  any  given  temperature  of  fuel  gases 
in  the  chimney,  must  not  be  lost  sight  of,  and  therefore  it  is  not  wise, 
if  chimney  draught  is  depended  upon,  to  reduce  the  temperature  of 

the  chimney  gases  below 
400°  F.  This,  however, 
leaves  200°  F.  under  ordi- 
nary working  conditions, 
that  may  be  usefully  em- 
ployed, and  in  a  great 
many  cases  where  fur- 
nace gases  arrive  at  the 
chimney  at  a  much  higher 
temperature  than  600°  F., 
it  leaves  a  very  much 
wider  margin. 


Economizers 

This  margin  of  tempe- 
rature is  made  use  of  to 
heat  the  feed  water  in  an 
apparatus  known  as  an 
economizer,  on  its  way  to 
the  boiler,  the  usual  ar- 
rangement, of  which  there 
are  several  variations, 
being  as  follows.  There 
are  a  number  of  iron  tubes 
fixed  vertically,  as  shown 
in  Figs.  51,  52,  and  53, 
in  a  brick  chamber  built 
for  them  at  the  back  of 
the  boilers,  the  chamber 
being  so  arranged  that 

the  flue  gases  can  be  obliged  to  pass  through  it,  or  can  be  allowed 
to  pass  by  a  flue  avoiding  the  economizer,  or  bye-pass,  directly  to  the 
chimney,  as  shown  in  Fig.  54.  The  water  to  be  heated  is  made  to 
circulate  through  the  vertical  pipes,  and  the  hot  gases  are  made  to  pass 
over  the  outside  of  the  pipes,  delivering  their  heat  to  them.  Two  diffi- 
culties arise  in  connection  with  this  arrangement :  the  hot  gases,  as  they 
are  cooled  by  delivering  up  their  heat  to  the  economizer  tubes,  deposit 


'f^mm^^m^^ 

FIG.  53. — Transverse  Section  of  Green's  Econo- 
mizer, showing  the  Tubes  and  enclosing  Brick- 
work. 


BOILER   ACCESSORIES 


the  finely  divided  carbon  known  as  soot,  and  which  is  usually  deposited 
as  a  lining  to  the  chimney,  upon  the  outside  surface  of  the  tubes. 
Carbon  in  the  finely  divided  state  is  a  very  poor  conductor  of  heat, 
for  the  reason  that  has  been  explained  in  an  earlier  portion  of  the 
book,  that  there  are  a  number  of  small  air  spaces  between  the 
particles  of  carbon,  which  offer  a  very  high  resistance  to  the  passage 
of  heat  currents.  Hence,  unless  the  deposit  of  soot  is  periodically 
removed  from  the  pipes,  the  efficiency  of  the  economizer  and  the 
heat  delivered  to  the  feed  water  would  very  speedily  be  reduced. 
To  accomplish  this,  all  economizers  have  scrapers  provided  on  the 


FIG.  54. — Plan  of  three  Lancashire  Boilers,  with  Green's  Economizers,  in  three 
groups  of  Tubes,  together  with  the  Chimney  and  the  Bye-pass,  or  Reserve  Flue. 

outside  of  the  tubes,  one  form  of  which  is  shown  in  Fig.  55,  and  the 
scrapers  are  kept  continually  moving  up  and  down  the  surface  of 
the  tubes,  constantly  removing  the  deposit  of  soot,  and  ensuring  that 
the  hot  gases  have  free  access  to  the  metal  surface,  the  soot  falling 
to  the  bottom  of  the  economizer  pit,  or,  in  some  forms  of  economizer, 
into  a  box  provided  for  it,  and  being  removed  periodically.  The 
scrapers  for  the  whole  of  the  tubes  in  an  economizer  are  worked  by 
chains  or  rods  actuated  by  gearing  fixed  above  the  tubes,  as  shown 
in  Fig.  51,  the  gearing  being  driven  by  a  small  engine  fixed  for  the 
purpose,  or  by  an  electric  motor,  the  latter  being  a  favourite  plan  in 


160    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


electricity  generating  works,  or  wherever  there  is  an  electricity  supply 
on  the  ground.  The  other  trouble  is  the  deposit  of  the  salts,  that 
are  carried  in  the  feed  water,  on  the  inside  of  the 
tubes.  This  is  provided  for  usually  by  removing 
the  salts,  by  means  of  water  softeners,  or  other 
methods,  before  the  water  enters  the  economizer. 
If  the  salts  are  not  removed,  a  crust  will  be  formed 
on  the  inside  of  the  tubes,  similar  to  that  which  is 
formed  on  the  water  surface  of  boilers,  that  must  be 
removed  from  time  to  time,  by  special  appliances. 

Green's  Economizer. — In  Green's  economizer, 
which  is  the  best  known,  and  which  is  shown  in 
Figs.  51  to  54,  the  tubes  are  all  made  to  one 
standard,  9  feet  in  length,  and  4-T%  inches  internal 
diameter.  The  tubes  are  built  into  sections,  and 
the  sections  built  into  batteries,  according  to  the 
quantity  of  water  that  the  economizer  is  to  deal 
with,  sixteen  tubes  being  the  unit.  The  capacity  of 
each  tube  is  6J  gallons,  and  it  is  recommended  by 
Messrs.  Green  that  the  whole  of  the  tubes  should 
be  emptied  every  hour;  or,  to  put  it  in  another  way, 
that  the  velocity  of  the  water  through  the  tubes 
should  be  at  the  rate  of  6]-  gallons  per  hour,  or 
about  -^-Q  of  a  gallon  per  minute.  This  rule  enables 
the  size  of  the  economizer  required  to  deal  with  the 
water  evaporated  by  any  boiler,  or  battery  of  boilers, 
to  be  easily  estimated,  by  the  following  formula : — 

1ST  =  W  x  6i 

where  N  is  the  number  of  tubes  required,  and  W  is  the  number  of 
gallons  of  water  per  hour  evaporated  by  the  boiler,  or  battery  of 
boilers. 

In  Messrs.  Carter's  economizers,  the  tubes  are  made  in  a  special 
form.  Two  tubes  of  a  special  section  are  cast  in  one,  with  a  con- 
necting passage  at  the  bottom,  and  an  opening  at  the  top,  for 
connection  to  the  box. 

In  the  Green's  economizer,  the  tubes  forming  a  section  are  forced 
by  hydraulic  pressure  into  the  top  and  bottom  "  boxes,"  which  are 
tubular  castings,  having  connecting  pieces,  for  the  entrance  of  the 
tubes. 

In  all  forms  of  economizers,  the  rule  which  applies  to  all  cases  of 
this  kind,  where  it  can  be  adhered  to,  is  adopted,  viz.  the  flue  gases 
and  the  water  to  be  heated  pass  through  the  apparatus  in  opposite 
directions,  the  hottest  water  meeting  the  hottest  gases,  and  the 
coldest  water  meetin  the  coldest  ases.  The  water  enters  the 


FIG.  55. — Eleva- 
tion and  Plan 
of  the  Scrapers 
employed  by 
Messrs.  Green 
on  their  Econo- 
mizers. The 
Scrapers  fit 
closely  on  the 
outside  of  the 
Tubes,  and  are 
kept  continu- 
ally moving  up 
anddown,scrap- 
ing  off  the  Soot. 


PLATE  OA. — Internal  View  of  Hoppes  Feed-water  Heater  and  Purifier.     The  Water 
.    passes  down  over  the  Trays  shown,  in  succession,  depositing  Foreign  Matter  in 
them. 


PLATE  QB. — Deposit  taken  from  a  Hoppes  3000  H.P.  Feed-water  Heater,  after  thirty 

days'  run. 


PLATE  9c. — Water  Tube  Boiler,  fitted  with  Hoppes  Feed-water  Heater.  The  Feed- 
water  Heater  is  shown  above  the  Boiler,  the  Water  from  it  entering  the  Boiler 
below  water  level.  The  Tank  shown  below  keeps  the  Heater  supplied  with 
Water.  [To  face  p.  160. 


BOILER  ACCESSORIES  161 

economizer  at  the  end  where  the  flue  gases  pass  to  the  chimney,  after 
having  given  up  a  large  portion  of  their  heat  to  the  water  in  the 
tubes,  and  the  water  leaving  the  economizer  at  the  point  where  the 
flue  gases  coming  directly  from  the  boiler,  enter  the  chimney  in 
which  the  tubes  are  fixed. 

There  appears  to  be  a  difference  of  opinion  between  the  makers 
of  economizers  as  to  the  advantage  of  keeping  the  water  in  the  tubes 
in  circulation.  Messrs.  Carter  have  designed  their  special  form  of 
apparatus  distinctly  with  the  object  of  keeping  the  water  in  circula- 
tion; and,  in  addition,  it  is  made  to  run  in  a  thin  stream  over 
a  thin  metal  surface,  on  the  opposite  side  of  which  are  the  flames 
of  the  hot  flue  gases.  Messrs.  Green,  on  the  other  hand,  state  that 
they  have  gone  very  carefully  into  this  matter,  and  that  they  do 
not  find  any  advantage  from  keeping  the  water  in  circulation.  It 
should  be  mentioned  that  the  water  is  maintained  in  circulation 
through  the  economizers  by  the  feed  pump,  but,  as  the  author  under- 
stands it,  Messrs.  Carter  provide  an  additional  circulation,  within 
the  economizer  itself,  and  break  up  the  mass  of  water  very  much 
more  than  Messrs.  Green  do.  In  Messrs.  Green's  apparatus,  each 
tube  contains  a  cylindrical  column  of  water  of  about  4^  inches  in 
diameter,  while  in  Messrs.  Carter's  the  water  is  only  in  a  very  thin 
stream. 

In  all  forms  of  economizer  it  is  now  usual  to  take  out  about  300° 
of  the  heat  of  the  flue  gases,  leaving  300°  to  350°  for  the  working  of 
the  chimney.  As  explained  in  connection  with  forced  draught,  it 
should  be  possible  to  considerably  reduce  this,  if  the  heat  could  be 
economically  employed,  and  improvement  would  appear  to  be  in  the 
direction  of  a  larger  absorption  of  the  heat  of  flue  gases,  where 
economizers  are  employed,  and  the  employment  of  a  smaller  number 
of  tubes. 

A  point  that  should  be  noted  in  connection  with  economizers  is 
given  by  Messrs.  Green.  Their  economizer  should  never  be  supplied 
with  water  at  a  lower  temperature  than  90°  F.  As  will  be  seen 
later,  the  difficulty  is  easily  overcome  by  interposing  a  steam  feed- 
water  heater  in  the  path  of  the  feed  water  on  its  way  from  the 
supply  to  the  economizer.  Where  this  cannot  be  arranged,  Messrs. 
Green  provide  a  modification  of  their  apparatus  in  which  the  water 
entering  the  economizer  is  heated  by  a  small  quantity  of  water  from 
the  hottest  water  of  the  economizer  itself. 

The  objection  to  supplying  the  economizer  with  feed  water  at 
less  than  90°,  is,  condensation  of  the  steam  that  is  present  in  the 
hot  gases,  and  of  the  gases  themselves,  take  place  if  water  below  this 
temperature  is  allowed  to  enter  the  tubes. 


i62     STEAM   BOILERS,   ENGINES,   AND   TURBINES 
Heating  Air  and  Water  by  Economizers 

It  was  mentioned  in  connection  with  the  Ellis  and  Eaves  system 
of  forced  draught,  that  air  for  the  boiler  furnaces  is  heated  by  the 
flue  gases.  In  a  modification  of  the  economizer  by  Messrs.  Green, 
it  is  arranged  to  heat  air  and  water  from  the  same  set  of  gases  on 
their  way  to  the  boiler.  Two  economizers  are  interposed  between 
the  backs  of  the  boilers  and  the  chimney,  one  for  heating  the  water, 
and  the  other  for  heating  the  air.  There  is  a  reserve  flue,  or  bye-pass, 
at  the  back  of  the  two  economizers,  leading  directly  from  the  main  flue 
at  the  back  of  the  boiler  to  the  chimney,  that  can  be  employed  when 
the  economizers  are  not  in  use.  The  two  economizers  are  very  similar 
in  construction,  but  water  passes  through  the  tubes  of  one,  and  air 
through  those  of  the  other,  the  hot  gases  passing  on  the  outside  of 
both  sets  of  tubes  in  succession,  the  water  heater  receiving  the  hot 
gases  first,  and  they  then  passing  to  the  air  heater.  A  fan  draws  the 
air  through  the  economizer  tubes  and  delivers  it  to  the  ashpit  or  the 
stoke-hold.  The  air  can  be  heated  to  any  desired  temperature,  accord- 
ing to  the  quantity  of  heat  that  can  be  abstracted  from  the  hot  gases, 
but  in  Messrs.  Green's  practice  it  appears  to  be  usual  not  to  heat  the 
air  more  than  200°.  It  must  be  remembered  that  if  air  and  water  are 
heated  by  economizers,  unless  a  larger  quantity  of  heat  is  abstracted 
from  the  flue  gases,  the  temperature  to  which  the  water  is  raised 
must  be  less  than  that  to  which  it  would  be  if  air  heating  was  not 
resorted  to  as  well,  and  as  in  other  cases,  it  becomes  a  question  as  to 
which  is  most  economical.  Eifty-five  cubic  feet  of  air  can  have  its 
temperature  raised  100°  for  100  heat  units,  while  only  1  Ib.  of  water 
will  have  its  temperature  raised  the  same  number  of  degrees  for  the 
same  number  of  heat  units.  The  problem  is  rather  a  practical  one, 
a*nd  has  to  be  worked  out  in  each  case. 

Certain  care  is  necessary  in  using  economizers.  In  frosty  weather, 
for  instance,  if  the  economizer  is  in  an  exposed  position,  where  the 
cold  will  penetrate  to  the  tubes,  they  should  not  be  left  full  of  water 
when  they  are  not  in  use,  as  otherwise  the  tubes  will  be  cracked  by 
the  expanding  ice  in  the  process  of  formation. 

Dampers  are  provided  at  each  end  of  the  bye -pass,  and  at  each 
end  of  the  economiser,  enabling  the  economisers  to  be  shut  off  when 
required,  and  they  should  be  shut  off  when  steam  is  not  being  taken 
from  the  boilers,  and  when  steam  is  being  got  up,  say  at  the  beginning 
of  a  working  day.  Messrs.  Green  recommend  that  the  draught  of 
the  boilers  should  be  regulated  by  the  main  damper  at  the  outlet  end 
of  the  economizer,  when  economizers  are  employed,  and  not  by  the 
boiler  damper,  and  that  the  outlet  valve  between  the  economizer  and 
the  boilers  should  not  be  closed  when  raising  steam,  nor  during  the 


BOILER   ACCESSORIES  163 

night,  or  at  meal  times,  and  that  the  boilers  should  be  fed  constantly, 
the  boiler  feed  valves  being  kept  open,  and  the  feed  being  regulated 
by  the  inlet  valve  of  the  economizer.  They  also  recommend  that 
cold  air  should  on  no  account  be  allowed  to  enter  the  economizer 
chamber.  Unfortunately,  as  mentioned  in  connection  with  draught, 
air  leakage  is  only  too  common  through  the  brickwork  of  boiler 
flues,  and  it  is  only  probable  that  the  same  thing  will  apply  to  the 
brickwork  of  the  economizer  chambers.  If  air  leakage  does  occur, 
it  will  lower  the  efficiency  of  the  economizer  by  lowering  the 
temperature  to  which  the  feed  water  or  the  air  is  raised,  because 
the  leakage  air  passing  into  the  economizer  chamber  will  rob  the  flue 
gases  of  a  portion  of  the  heat  that  would  otherwise  pass  to  the 
economizer  tubes,  the  air  being  itself  raised  to  the  temperature  of 
the  flue  gases,  and  there  being  that  much  less  heat  available  for 
heating  the  feed  water,  or  the  air  for  the  boiler  furnace.  Eemember- 
ing,  again,  that  55  cubic  feet  of  air  raised  100°  in  temperature,  robs 
the  flue  gases  of  100  heat  units,  and  that  it  is  quite  possible  to  have 
a  good  many  lots  of  55  cubic  feet  entering  the  economizer  chamber 
through  cracks  in  the  brickwork  and  imperfect  mortaring,  etc.,  and 
it  will  not  be  difficult  to  see  how  easily  losses  can  arise. 


Steam  Feed=Water  Heaters 

The  apparatus  to  be  described  here  are  known  generically  as  feed- 
water  heaters,  but  the  author  prefers  to  call  them  steam  feed- water 
heaters,  in  order  to  distinguish  them  from  the  economizer,  which,  it 
will  be  seen,  is  also  a  feed-water  heater.  There  are  two  types  of 
steam  feed-water  heater,  the  enclosed  and  the  open  type. 


The  Enclosed  Steam  Feed -Water  Heaters 

The  arrangement  of  the  enclosed  type  of  feed-water  heater  is  very 
similar  to  that  of  the  economizer,  but  very  much  smaller,  and  steam 
is  used  in  the  place  of  the  hot  gases.  The  apparatus  consists  usually 
of  a  cylinder,  or  in  some  cases  of  a  rectangular  box,  with  a  number  of 
tubes  held  between  tube  plates  inside,  and  a  space  at  each  end. 
There  is  a  space  all  round  the  tubes,  and  also  between  them.  The 
arrangement  of  feed- water  heaters  varies.  In  the  majority  of  cases 
the  water  to  be  heated  passes  through  the  tubes,  while  the  steam 
that  is  to  heat  it  passes  through  the  space  surrounding  them.  In 
some  cases  the  reverse  arrangement  rules,  the  steam  passing  in  the 
tubes,  and  the  water  passing  on  the  outside.  Exhaust  steam  from 
the  engines  or  turbines  is  sometimes  employed  for  heating  the  feed 


164    STEAM   BOILERS,   ENGINES,   AND  TURBINES 


water,  either  on  its  way  to  the  condenser,  or  to  the  atmosphere,  but 
more  commonly  that  from  steam  pumps  or  other  auxiliaries.  It 
is  a  disputed  question  whether  the  exhaust  steam  from  condensing 
engines  should  be  employed  for  heating  the  feed  water,  the  objection 
being  that  the  steam  will  be  throttled  and  a  back  pressure  set  up  in 
the  steam  cylinder  or  the  turbine.  Messrs.  Eoyle  of  Irlam,  and 
other  firms,  recommend  that  feed-water  heaters  should  be  employed 
between  the  low-pressure  cylinder  and  the  condenser,  and  they  claim 
that  no  back  pressure  will  be  produced,  providing  that  the  steam- way 
is  sufficiently  large ;  and  in  their  apparatus  they  state  that  the  area 

of  the  steam  passages  within  the  heater  is 
several  times  that  of  the  steam  pipe. 

Live  steam  from  the  boiler  is  also 
frequently  employed  where  exhaust  steam 
||  is  not  available,  as  it  is  found  that,  though 
additional  coal  must  be  burned  to  furnish 
the  steam  required  to  heat  the  feed  water, 
and  it  looks  as  though  it  should  be  more 
economical  to  burn  the  coal  to  heat  the 


FIG.  56.— The  Kiblet  Steam- 
feed  Water  Heater.  The 
Water  passes  through  the 
Tubes  and  the  Steam  on 
the  outside. 


FIG.  57. — The  Hardwick  Steam- 
feed  Water  Heater.  The  Water 
passes  through  the  Tubes  as 
shown. 


water  directly  in  the  boiler  itself,  the  losses  arising  from  defective 
circulation,  if  cold  feed  water  is  pumped  into  the  boiler,  are  so  great 
that  the  economy  is  on  the  side  of  the  live  steam  heater. 


BOILER  ACCESSORIES 


165 


In  addition,  where  high  boiler  pressures  are  employed,  as  from 
150  to  200  Ibs.  per  square  inch,  and  the  engines  or  turbines  are 


FIG.  58. — Boyle's  Feed-water  Heater. 


FIG.  59. — Vertical  Transverse  Section 
of  Messrs.  Royle's  Feed -water 
Heater,  showing  the  specially 
formed  Tubes  employed. 


worked  to  the  best  advantage  expansively,  the  exhaust  steam  has  not 
sufficient  heat  remaining  in  it  to  raise  the  temperature  of  the  feed 


1 66     STEAM   BOILERS,   ENGINES,  AND   TURBINES 

water  to  that  of  the  water  in  the  boiler.  Thus,  according  to  Messrs. 
Holden  &  Brooke's  experience,  with  a  boiler  pressure  of  150  Ibs., 
while  the  temperature  of  the  water  in  the  boiler  is  365°  F.,  the 
temperature  of  the  feed  water  heated  by  the  exhaust  steam  is  only 
180°,  and  in  these  cases  if  only  feed- water  heaters  are  employed  live 
steam  must  be  used.  If,  however,  economizers  are  employed,  it  will 
be  evident  that  the  feed-water  heater  is  a  useful  auxiliary  to  the 
economizer,  raising  the  temperature  of  the  water  considerably  above 
the  minimum  temperature  at  which  it  should  enter  the  economizer. 

Some  forms  of  feed- water  heaters  are  shown  in  Figs.  56  to  61. 
The  arrangement  of  the  tubes  in  the  feed-water  heaters  are  various. 
Vertical  tubes  are  very  much  in  favour,  as  shown  in  Figs.  56  and 
57,  but  horizontal  coils  of  tubes  are  also  employed,  and  are  made  by 
the  National  Pipe  Bending  Company  of  Newhaven,  Connecticut. 

The  tubes  also  are  various  in  form.  The  "Bow"  tube,  made  by 
Messrs.  Eoyle  of  Irlam,  Manchester,  is  shown  in  Figs.  58  and  59. 
As  will  be  seen,  it  is  an  ordinary  tube  indented  at  equal  distances 
throughout  its  length,  alternate  indentations  being  at  right  angles  to 
each  other,  and  each  indentation  being  the  same  on  opposite  sides  of 
the  tubes.  The  indentations  produce  a  very  flexible  tube,  and  it  is 
claimed  by  Messrs.  Boyle  that  the  surface  over  which  the  water  passes 
being  larger,  the  transmission  of  heat  from  the  steam  to  the  water  is 
more  rapid  with  their  tube  than  with  the  ordinary  vertical  or  coiled 
tube. 

Another  form  of  tube  for  feed-water  heaters  is  the  Wainwright 
corrugated  tube,  made  by  the  Alberger  Condenser  Company  of  New 
York.  In  Fig.  60  is  given  heat-absorption  curves  with  plain  tubes, 
and  Wainright  corrugated  tubes,  showing  the  claims  made  by  the 
Alberger  Company  on  its  behalf.  Messrs.  Holden  &  Brooke  make  a 
special  form  of  feed- water  heater  for  use  with  live  steam.  It  is  shown 
in  section  in  Fig.  61,  and  the  special  feature  is  a  system  of  con- 
centric tubes  arranged  so  that  the  feed  water  passing  through  the 
apparatus  has  to  flow  in  a  very  thin  stream  through  the  annular  space 
between  the  concentric  tubes,  steam  being  present  on  each  side  of  the 
annular  space.  From  the  figure  it  will  be  seen  that  there  is  the 
usual  cylindrical  main  body  with  two  sets  of  tube  plates,  the  longer 
tubes  being  held  by  the  top  and  bottom  plates  and  the  shorter  tubes 
by  the  intermediate  plates.  There  is  also  a  diaphragm  between  the 
two  lower  tube  plates.  As  will  be  seen  from  the  drawing,  the  water 
enters  by  the  inlet  on  the  right,  and  is  obliged  to  pass  up  through 
the  annular  spaces  shown,  down  again  through  the  annular  space  in 
another  set  of  tubes,  and  so  on,  passing  out  by  the  outlet  on  the  left, 
after  having  flowed  through  all  the  spaces  between  the  concentric 
tubes.  It  will  be  seen  also  that  there  is  only  a  live  steam  inlet  but 
no  outlet,  the  full  latent  heat  being  taken  out  of  the  steam,  and  it 


BOILER  ACCESSORIES 


.67 


being  condensed  after  it  has  done  its  work,  the   condensed  water 
being  allowed  to  flow  away  by  the  drain  at  the  bottom. 

The  feed- water  heater  acts  to  a  certain  extent  as  a  purifier  for  the 
feed  water,  inasmuch  as  a  certain  portion  of  the  substances  that  are 
held  in  suspension  in  the  feed  water  are  thrown  down  when  the  water 


HEAT  ABSORPTION  CURVES 


aw 
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300 
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200 

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VELOCITY  OF  WATER  IN  FT.  PER  WIN. 

SCUM 


WATER 
INLET 


.  60. — Wainwright's  Curves  for  the 
.Relative  Heating  Effect  realized  with 
Plain  and  with  Corrugated  Tubes. 


DRAIN 

FIG.  61. — Messrs.  Holden  &  Brooke's  Live  Steam- 
feed  Water  Heater.  The  Water  passes  in  the 
annular  space  between  the  two  sets  of  Tubes 
shown,  the  Steam  passing  on  both  sides. 


is  raised  to  a  certain  temperature,  also  some  of  the  salts  which  cause 
what  is  known  as  the  hardness  in  water  are  also  thrown  down; 
and  in  the  best  forms  of  feed- water  heaters,  arrangements  are  made  in 
the  water  spaces  for  the  deposit  of  the  solid  matters  that  are  thrown 
down,  and  their  removal  from  time  to  time  through  an  aperture  pro- 
vided for  the  purpose.  The  usual  arrangement  is  that  shown  in 


i68    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

Fig.  56,  where  the  deposit  falls  to  the  bottom  of  the  water  space 
in  the  base  of  the  apparatus,  and  is  drawn  off  by  the  cock  shown. 


Open  Steam  Feed -Water  Heaters 

The  open  feed- water  heater  is  something  on  the  lines  of  the  jet 
condenser,  to  be  described  later  on.  It  consists  primarily  of  a  vessel 
into  which  the  water  to  be  heated  is  delivered,  usually  in  the  form  of 
a  spray,  and  there  it  meets  the  exhaust  steam,  the  latter  giving  up  its 
latent  heat  to  the  water  and  raising  its  temperature.  It  will  be 
understood  that  this  apparatus  is  more  economical  in  heat  than  the 
closed  form  of  the  feed-water  heater,  because  the  whole  of  the  heat  of 
the  steam  is  delivered  to  the  water  in  this  form,  whereas  only  a  portion 
is  delivered  in  the  case  of  the  closed  heater.  The  objection  to  its  use 
is  that  which  is  mentioned  later  in  connection  with  the  purification 
of  feed  water— the*  fact  that  the  steam  from  reciprocating  engines 
always  carries  a  certain  quantity  of  oil  in  a  finely  divided  state,  and 
this  being  delivered  to  the  feed  water  is  carried  over  into  the  boiler 
unless  means  are  taken  to  separate  it  afterwards.  On  the  other 
hand,  some  firms  advise  the  use  of  this  form,  or  of  the  closed  form  of 
heater  in  which  the  steam  passes  through  the  tubes,  where  the  feed 
water  contains  considerable  quantities  of  foreign  matter  or  other  im- 
purities. This,  however,  has  led  to  the  development  of  special  classes 
of  combined  feed- water  heaters  and  purifiers,  of  which  the  Hoppes, 
made  by  the  Hoppes  Manufacturing  Company  of  Springfield,  Ohio, 
is  one  of  the  best  known.  In  the  Hoppes  apparatus,  which  is  shown 
on  Plate  9A,  there  is  the  usual  containing  cylinder,  fixed  horizontally, 
and  containing  trough- shaped  trays,  or  pans  of  thin  sheet  steel,  placed 
one  above  the  other.  The  water  to  be  purified  and  heated  is  pumped 
into  the  upper  tray.  It  is  allowed  to  fill  the  upper  tray  and  then  trickle 
over  the  edge  of  the  tray  down  the  outside,  and  from  the  lowest  part 
of  the  tray  into  the  next  one,  which  it  gradually  fills,  trickling  down 
the  outside  of  the  second  tray  into  the  third,  which  it  fills,  and  so  on. 
Exhaust  steam  or  live  steam  is  led  to  the  cylinder,  heating  the  water 
in  the  same  manner  as  with  other  heaters,  the  water,  after  it  has  been 
heated  being  usually  allowed  to  descend  by  gravity  to  the  boiler  it  is 
feeding,  and  being  led  into  the  boiler  below  the  water  level.  It  is 
stated  that  Mr.  Hoppes  took  the  idea  of  the  apparatus  from  the 
well-known  action,  so  often  seen  in  caves,  by  which  stalactites  and 
stalagmites  are  built  up.  The  salts  and  other  foreign  substances 
contained  in  the  water  are  deposited  upon  the  steel  troughs,  upon 
which  they  gradually  grow,  the  water  passing  on  purified  and  heated. 
Plate  9s  shows  the  deposit  taken  from  a  Hoppes  feed-water  heater 
fitted  to  a  3000  horse-power  plant  after  thirty  days'  run.  Plate  9c 


BOILER   ACCESSORIES 


169 


QTEfJM   -PIPE 


f££O  PUMP 


shows  the  arrangements  for  fixing  the  Hoppes  apparatus  to  a  water- 
tube  boiler. 

The  Simms  Company  of  Erie,  Pennsylvania,  also  make  an  open 
feed-water  heater,  somewhat  resembling  the  Hoppes  purifier,  with 
which  a  filter  is  combined.  It  consists  of  the  usual  vertical  cylinder, 
having  trays  in  the  upper  portion,  the  trays  being  slightly  inclined 
to  the  horizontal,  and  the  water 
being  made  to  pass  over  the 
trays  in  succession  as  it  descends. 
The  trays  are  heated  by  steam. 
The  water,  after  passing  over  the 
trays  and  being  heated,  and  to 
a  certain  extent  purified,  passes 
through  a  coke  filter  at  the 
bottom,  and  from  thence  is  taken 
to  the  boiler.  It  should  be  noted 
that  where  feed-water  heaters  are 
connected  to  pumps  there  should 
be  an  air  vessel  attached  and  a 
relief  valve.  The  air  vessel  pro- 
vides a  cushion  against  the  stroke 
of  the  pump,  and  the  relief  valve 
prevents  the  apparatus  being 
subject  to  too  high  a  pressure. 

The  question  of  what  water  shall  be  employed  in  the  feed-water 
heater  is  often  an  important  one.  In  some  cases  the  condensed  steam 
water  from  a  hot  well,  into  which  it  is  discharged  from  the  condenser, 
is  employed,  and  in  others  a  portion  of  the  circulating  water  from  the 
surface  condensers,  which  has  already  been  heated  to  a  certain  extent, 
is  used.  The  objection  to  the  condensed  water  from  the  hot  well  is 


FIG.  62. — Diagram  showing  the  Course  of 
the  Steam  and  Water,  where  the  Con- 
densed Steam  is  employed  for  the 
Boiler  Feed. 


FIG.  63. — Diagram  showing  the  arrangement  where  a  portion  of  Circulating  Water 
from  the  Condenser  is  employed  as  Feed  Water  for  the  Boiler,  after  being  heated 
by  Exhaust  Steam  and  the  Flue  Gases.  The  remainder  of  the  Circulating  Water 
is  allowed  to  run  away,  or  is  carried  to  the  Cooling  Tower. 

that  already  mentioned — with  reciprocating  engines  the  exhaust  steam 
contains  oil.  This  does  not  apply  to  exhaust  steam  from  turbines  nor 
to  the  water  that  has  been  used  in  a  surface  condenser.  Fig.  62 
is  a  diagram  showing  the  course  of  the  water  and  steam  where  the 
condensed  steam  is  used  to  feed  the  boiler,  without  any  intervening 
apparatus ;  Fig.  63  the  arrangement  where  a  portion  of  the  circulating 


1 70    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

water  from  the  condenser  is  used  for  the  feed,  and  is  heated  by  pass- 
ing through  feed  waters  and  economizers. 

Feed = Water  Pumps 

The  feed  water,  it  will  be  understood,  has  to  be  forced  into  the 
boiler  against  the  pressure  of  the  steam  in  the  boiler,  which,  it  will 
be  remembered,  is  communicated  through  the  water  and  the  steam  in 
every  direction,  and  therefore  some  form  of  pump  or  other  apparatus 
has  to  be  employed  that  will  produce  a  pressure  sufficient  to  over- 
come the  boiler  pressure.  Broadly,  feed-water  pumps  are  on  two 
lines.  The  ordinary  ram  or  plunger  pump  of  the  two  or  three  throw 
type  is  often  employed,  driven  by  its  own  engine  or  by  an  electric 
motor ;  and,  again,  special  forms  of  feed  pumps  have  been  worked 
out  by  different  firms,  designed  especially  for  the  work.  Injectors, 
described  on  p.  173,  are  also  being  used  in  place  of  feed  pumps. 

Ram  Pumps 

In  the  ram  or  plunger  pump  there  are  one  or  more  cylinders  ; 
usually,  in  the  case  of  feed  pumps,  three  cylinders,  which  may  be 
fixed  either  vertically  or  horizontally,  as  convenient,  each  cylinder 
having  a  ram  or  plunger,  which  is  virtually  a  piston  moving  to  and 
fro  inside  the  cylinder,  just  as  the  piston  of  a  steam  engine  moves  in 
its  cylinder.  As  the  plunger  rises,  the  suction  valve  in  the  bottom 
of  the  cylinder  opens  inwards  and  allows  the  water  from  the  suction 
pipe  to  pass  into  the  cylinder.  On  the  return  stroke  of  the  plunger, 
the  weight  of  the  water  above  it  closes  the  suction  valve,  and  the 
force  exerted  by  the  plunger  opens  the  delivery  valve,  which  opens 
outwards  into  the  feed  pipe,  leading  either  directly  to  the  boiler  or  to 
the  feed-water  heater  or  economizer.  Messrs.  Frank  Pearn  also 
make  a  double-acting  boiler  feed  ram  pump.  The  plungers  of  the  ram 
pumps  are  moved  by  rods  attached  to  them,  similar  to  piston  rods, 
the  other  ends  of  the  rods  being  fixed  to  a  crank  forming  part  of  a 
shaft,  to  which  a  pulley  is  attached,  or  that  is  directly  connected  to 
the  revolving  shaft  of  a  steam  engine  or  electric  motor.  When  there 
are  two  or  more  cylinders  the  cranks  of  the  cylinders  are  arranged 
with  two,  either  90°  or  180°  apart,  and  with  three  120°  apart,  so  that 
the  effort  made  by  the  engine  is  evenly  distributed  throughout 
the  revolution. 

Special  Pumps 

Special  feed  pumps  are  of  various  forms,  designed  principally  to 
occupy  small  space  and  to  work  automatically.  The  Worthington  is 


BOILER   ACCESSORIES  171 

one  of  the  best  known.  It  is  a  steam-driven  pump;  that  is  to  say, 
there  is  a  steam  cylinder  and  a  water  cylinder  fixed  on  one  bed-plate, 
the  two  cylinders  forming  part  of  one  casting,  and  the  piston  of  the 
steam  cylinder  and  the  plunger  of  the  pump  being  connected  by  one 
piston-rod.  The  steam  cylinder  receives  steam  from  the  boiler,  or 
when  steam  is  first  being  raised,  from  the  auxiliary  or  donkey  boiler. 
The  pump  cylinder  is  usually  arranged  double-acting,  as  it  is  called. 
It  draws  in  water  into  one  portion  of  the  pump  cylinder  as  the  ram 
moves  it  in  one  direction,  and  at  the  same  time  forces  water  that  was 
drawn  in  at  the  previous  stroke  through  the  delivery  valve  of  the 
other  portion.  As  the  piston  of  the  steam  cylinder  returns,  the 
water  that  was  drawn  in  on  the  out-stroke  is  forced  out  through  the 
delivery  valve  on  that  side,  and  water  is  drawn  in  to  the  other 
portion  of  the  pump  chamber.  In  the  Worthington  pump  there  are 
two  complete  sets  of  steam  and  water  cylinders,  standing  side  by  side, 
and  it  is  arranged  by  means  of  a  swinging  rod  that  the  action  is  auto- 
matic :  the  rod  of  one  pump  actuates  the  valve  on  the  steam  cylinder 
of  the  other  pump,  causing  reversal  of  motion  at  the  proper  time, 
the  steam  cylinders  being  fitted  with  slide  valves.  The  slide  valve 
is  explained  in  the  chapter  on  "  Steam  Engines." 


The  Pulsometer  Feed  Pump 

The  pulsometer  pump  is  quite  different  from  the  usual  run  of 
pumps.  It  contains  two  chambers  side  by  side,  openiog  on  to  one 
steam  pipe  at  the  top,  and  having  suction  and  delivery  valves  at  the 
bottom.  The  connection  between  each  of  the  chambers  and  the 
steam  pipe  is  closed  or  opened  by  the  motion  of  a  spherical  ball. 
When  the  ball  is  on  the  left,  say,  the  admission  of  steam  to  the 
left-hand  chamber  is  cut  off,  while  the  steam  is  free  to  enter  the 
right-hand  chamber,  and  the  action  of  the  apparatus  is  as  follows : — 
Supposing  the  ball  to  be  on  the  left  and  the  left-hand  chamber  to  be 
empty,  a  partial  vacuum  having  been  created  by  the  condensation  of 
the  steam  with  which  the  chamber  was  previously  filled,  the  water 
that  is  to  be  pumped  runs  into  the  chamber  up  to  a  certain  height. 
Meanwhile  steam  has  been  entering  the  right-hand  chamber  and 
forcing  the  water  that  was  in  the  chamber  out  through  the  delivery 
valve,  and  when  the  level  of  the  water  has  reached  the  entrance 
to  the  delivery  valve,  the  steam  above  is  condensed  and  the  ball  at 
the  top  then  rolls  over  and  shuts  off  the  supply  of  steam  to  the 
right-hand  chamber,  the  steam  then  entering  the  left-hand  chamber, 
forcing  the  water  in  front  of  it  through  the  delivery  valve,  the 
suction  valve  having  closed  immediately  the  pressure  of  steam  com- 
menced. When  the  water  reaches  the  level  of  the  delivery  valve, 


172    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  steam  in  the  left-hand  chamber  rapidly  condenses,  the  lowered 
pressure  resulting  causing  the  ball  to  roll  over  to  that  side,  shutting 
off  the  steam  on  that  side,  the  steam  now  entering  the  other  side, 
which  has  meanwhile  been  filled  up  with  water.  The  action  of  the 
apparatus  goes  on  continuously  as  long  as  steam  is  supplied  to  it.  It 
is  of  great  service  where  the  water  contains  foreign  matter,  as  the 
valve  does  not  clog  as  the  valves  of  some  pumps  do.  The  ball  valve 
as  it  rolls  over  and  over,  maintains  itself  and  its  seat  in  proper  order, 
and  keeps  the  steam  passages  as  they  should  be. 

There  are  two  or  three  other  pumps  that  have  been  designed  on 
the  lines  of  the  pulsometer,  known  by  various  names,  that  are  also 
available  for  boiler  work.  The  pulsometer  can  be  used  in  positions 
where  it  would  sometimes  be  difficult  to  use  other  pumps,  such  as  on 
a  dockside  and  by  the  side  of  a  river,  and  so  on,  being  able  to 
work  when  completely  immersed. 


Electrically  driven  Boiler  Feed  Pumps 

The  great  objection  to  some  forms  of  steam  feed  pumps  is  the 
large  quantity  of  steam  they  consume — as  much  as  200  to  250  Ibs. 
per  indicated  horse-power  in  the  steam  cylinders.  The  same  com- 
plaint in  a  minor  degree  is  made  against  the  engines  driving  three- 
throw  feed  pumps,  since  all  small  steam  engines  are  wasteful  in  steam 
consumption,  and  this  has  led  to  the  adoption,  wherever  electrical 
power  is  available,  of  the  electric  drive.  On  the  other  hand,  some 
engineers  do  not  like  the  electric  drive,  especially  in  electricity 
generating  works,  because  if  there  is  a  large  demand  for  current, 
leading  to  a  certain  fall  of  pressure  in  the  generating  station,  the  feed 
pumps  are  apt  to  feel  it  and  to  slow  up  more  or  less,  while  the  boilers 
require  feeding  more  energetically  in  order  to  keep  up  the  supply  of 
steam.  It  is  possible,  of  course,  to  provide  for  this  by  suitable 
arrangements  at  the  switch-board.  Another  objection  made  by 
engineers  of  works  that  are  stopped  at  night  and  from  Saturday  to 
Monday  is — the  electrically  driven  pump  cannot  run  until  sufficient 
steam  is  made  to  drive  a  generator,  while  the  steam  pump  can  nearly 
always  be  driven  from  a  small  auxiliary  boiler.  On  board  ship  what 
is  called  a  "  donkey  "  boiler  is  always  carried  for  this  very  purpose, 
and  for  use  when  the  ship  is  in  dock.  It  is  a  small  boiler,  sometimes 
of  the  vertical  type,  something  on  the  lines  of  a  multitubular  land 
boiler,  in  which  steam  can  be  got  up  very  quickly,  and  which  is 
employed  for  handling  cargo,  winches,  etc.,  and  its  steam  is,  of  course, 
available  for  anything,  such  as  steam  pumps,  that  may  require  it. 
In  the  electrically  driven  boiler-feed  pump  an  electric  motor  is 
mounted  on  the  frame  of  the  pump,  and  its  axle  is  geared  to  that  of 


BOILER   ACCESSORIES  173 

the  pump  by  spur  and  pinion  gearing  in  the  required  ratio.  The  motor 
is  supplied  with  current  from  the  main  switch-board,  and  its  speed 
can  be  regulated  by  varying  the  current  passing  in  its  field  magnet 
coils. 

Donkey  or  Wall  Pumps 

The  wall  pump,  or  the  "  donkey  "  pump,  as  it  is  sometimes  called, 
is  a  very  favourite  form  of  boiler-feed  pump,  because  it  can  be  fixed 
in  some  convenient  position  out  of  the  way. 

As  its  name  implies,  it  is  fixed  against  the  wall  of  the  building, 
and  usually  carries  the  steam  and  water  cylinders  on  one  casting, 
which  also  forms  the  bracket  or  bed-plate  by  which  it  is  secured  to 
the  wall,  and  there  is  also  usually  a  small  flywheel.  In  one  form, 
made  by  Messrs.  Pearn,  the  steam  cylinder  is  above,  with  its  slide 
valve,  the  water  cylinder  being  below,  and  the  air  vessel  required 
with  pumps  is  between  the  cylinders  and  the  suspending  bracket, 
the  crank  shaft  and  the  fly-wheel  being  supported  by  a  loop  from 
the  junction  of  the  steam  and  water  piston  rods. 


Injectors 

The  injector  is  another  apparatus  used  for  delivering  the  feed 
water  to  the  boiler.  It  acts  as  pump  and  feed-water  heater.  It 
operates  upon  what  is  known  as  the  injector  principle,  the  most 
familiar  example  of  which  is  the  scent  spray.  Whenever  air,  steam, 
or  gas  is  forced  across  the  surface  of  a  pipe  containing  either  water, 
air,  or  gas,  the  friction  of  the  air,  or  steam,  on  the  surface  of  the  water, 
or  air  in  the  pipe,  causes  a  small  portion  to  be  drawn  out  of  the  pipe 
and  to  be  forced  along  in  the  direction  in  which  the  stream  of  air  or 
steam  is  passing.  The  passage  outwards  of  the  small  quantity  of  air 
or  water  causes  a  lowered  pressure  within  the  pipe,  this  again  causing 
the  water  or  the  air  in  the  pipe  to  rigfc,  and  a  small  portion  again  to  follow 
the  first  portion,  and  so  a  continuous  stream  is  set  up  as  long  as  the 
air  or  steam  is  passing  across  the  mouth  of  the  pipe.  Similarly,  if  a 
stream  of  air,  or  steam,  or  gas,  is  forced  through  a  passage  in  which  it 
is  surrounded  either  by  air,  water,  or  steam,  a  similar  action  takes 
place,  the  water  or  the  air  following  the  original  stream,  and  a 
continuous  stream  being  set  up.  The  steam  jets  that  have  been 
described  as  inducing  currents  of  air  for  furnace  draught  act  on  this 
principle.  The  jet  of  steam  draws  a  small  quantity  of  the  air  by 
which  it  is  surrounded  along  with  it  in  the  direction  in  which  it  is 
going,  that  lowering  the  pressure  behind  it,  and  the  pressure  of  the 
atmosphere  outside  forcing  a  continuous  current  of  air  along  mingling 


i74    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


with  the  steam  jet.  In  the  case  of  the  steam  injector,  which  is  under- 
stood to  mean  an  apparatus  for  delivering  a  stream  of  water,  a  steam  jet 
passes  through  a  nozzle,  as  shown  in  Fig.  64,  and  the  nozzle  is  sur- 
rounded by  water,  as  seen.  The  passage  of  the  steam  jet  causes  a 
small  quantity  of  air  to  accompany  it  in  the  direction  in  which  it  is 
going,  this  lowering  the  pressure  in  front  of  the  water  surrounding 
the  steam  nozzle.  The  pressure  behind  the  water  then  forces  the  water 
around  the  nozzle  forwards  to  take  the  place  of  the  air  which  has  moved 
forwards,  and  a  contin- 
uous stream  of  water 
mixed  with  the  steam, 
and  therefore  heated  by 
the  steam  is  the  result. 


FIG.  64.— Sectional  Drawing  of 
Reverberatory  Steam  Injector. 
R  is  the  Steam  Nozzle,  S  the 
Cone  through  which  the  Water 
is  drawn  by  the  Steam.  The 
Steam  Nozzle  is  surrounded  by 
the  Water  Stream. 


FIG.  66.— Section  of  Messrs.  Davies  &  Metcalfe's  In- 
jector in  which  Exhaust  Steam  and  Live  Steam 
from  the  Boiler  are  employed.  There  are  Two 
Steam  Cones,  one  inside  the  other,  both  sur- 
rounded by  the  Outer  Cone. 


The  pressure  in  the  boiler  against  which  the  steam  injector  is  able 
to  work  may  be  very  much  greater  than  that  of  the  pressure  of  the 
steam  passing  in  the  nozzle  of  the  injector,  the  reason  of  this  being 
that  a  portion  of  the  energy  carried  by  the  steam  in  the  nozzle,  in  the 
form  of  velocity  head,  is  converted,  on  meeting  the  stream  of  water, 
into  pressure  head,  and  in  that  way  the  pressure  available  for  forcing 
the  water  into  the  boiler  is  considerably  increased.  With  exhaust 
steam,  for  instance,  at  only  atmospheric  pressure,  the  injector  is  made 


BOILER   ACCESSORIES 


175 


to  feed  into  boilers  working  at  as  much  as  95  Ibs.  per  square  inch, 
while  with  the  assistance  of  a  small  jet  of  live  steam  from  the  boiler 
itself,  as  will  be  explained,  the  feed  is  accomplished  up  to  pressures 
as  great  as  300  Ibs.  per  square  inch. 

It  will  be  understood  that  this  is  another  case  of  the  conversion  of 
energy  from  one  form  to  another.     The  apparatus,  sections  of  which 
are  shown  in  Figs.  64, 65, 66,  and  67, 
consists  of  two  cones,  one  carrying 
steam  nozzle  and  the  other  being 
arranged  as  a  combining  chamber,  m -\\^m  /  •   '  i, 

B     P          ^":^ 

.!-l4       \.4 


-- 


DELIVERY 


;FiG.  66 — Section  of  Messrs.  Holden  and  Brooke's 
Injector  for  Live  Steam  and  Exhaust  Steam. 


FIG.  67. — Messrs.  Holden  and  Brooke's  In- 
jector for  Exhaust  Steam,  in  which  both 
Water  and  Steam  are  controlled  by  One 
Handle. 


where  the  steam  and  water  join  to  pass  on  to  the  delivery  port. 
The  water  inlet,  as  will  be  seen,  surrounds  the  cone  carrying  the 
steam  nozzle,  and  it  is  arranged,  when  the  injector  is  started,  that 
steam  is  admitted  at  the  same  time  as  a  certain  flow  of  water  is  also 
admitted,  and  a  stream  of  water,  heated  by  the  steam  and  passing 
to  the  delivery  port,  is  gradually  formed.  It  will  be  noticed  that 
there  is  an  overflow  aperture  shown  in  the  drawings.  This  is  for  the 
purpose  of  allowing  the  passage  of  the  water  which  first  passes 


176    STEAM   BOILERS,   ENGINES,   AND  TURBINES 

through  the  apparatus,  and  which  is  not  heated  and  has  not  come 
under  the  influence  of  the  moving  jet  of  steam,  to  pass  harmlessly 
away.  When  the  stream  is  set  up,  the  overflow  ceases,  and  should 
the  steam  jet  fail  from  any  cause,  and  therefore  the  stream  of  water 
passing  to  the  boiler  be  broken,  the  water  coming  from  the  water 
inlet  passes  by  way  of  the  overflow. 

It  will  be  understood  that,  as  usually  arranged,  there  are  two 
pipes  leading  to  the  injector,  one  bringing  steam  and  the  other  bring- 
ing the  water,  as  shown,  and  a  third  leading  to  the  boiler,  carrying 
the  heated  feed  water,  the  steam  and  water  pipes  having  their  own 
controlling  cocks.  In  some  forms  of  apparatus,  however,  the  whole 
arrangement  is  combined  in  one,  with  one  controlling  handle  or  regu- 
lator, the  steam  nozzle  and  the  water  supply  being  connected  together 
by  a  coarse-pitched  thread,  both  of  which  are  moved  by  the  regulator 
handle,  as  shown  in  Fig.  67.  As  explained  above,  the  injector  is 
worked  by  exhaust  steam,  where  that  is  available,  but  it  is  also 
worked  by  live  steam  directly  from  the  boiler,  and,  as  mentioned,  also 
by  a  combination  of  live  steam  and  exhaust  steam.  In  one  form  of 
the  latter,  made  by  Messrs.  Davies  &  Metcalfe,  shown  in  Fig.  65,  there 
is  a  second  steam  nozzle,  inside  the  first,  and  of  very  much  smaller 
bore,  this  smaller  nozzle  being  supplied  with  live  steam  from  the 
boiler,  and  its  office  is  to  act  as  an  injector  upon  the  exhaust  steam, 
just  as  the  ordinary  steam  jet  acts  upon  air  or  water  through  which 
it  is  passing.  The  small  jet  of  live  steam  causes  a  larger  quantity 
of  exhaust  steam  to  be  carried  into  the  apparatus,  this  enabling  the 
water  to  be  forced  into  the  boiler  at  a  higher  pressure  than  would 
otherwise  be  possible.  Messrs.  Holden  &  Brooke  also  make  an 
apparatus  in  which  live  steam  is  used  as  a  supplementary  injector. 
It  is  shown  in  section  in  Fig.  66,  and  from  the  drawing  it  will  be 
seen  that  the  delivery  passage  of  the  exhaust-steam  injector  forms 
the  inlet  for  the  auxiliary  live-steam  injector,  the  live  steam  forcing 
the  already  heated  water  from  the  exhaust-steam  injector  into  the 
boiler  at  a  higher  pressure,  and  with  a  higher  temperature. 

In  practically  all  forms  of  injector,  the  regulation  of  the  water 
supply  is  carried  out  by  the  position  of  the  steam  nozzle.  In  Messrs. 
Holden  &  Brooke's  combined  apparatus,  the  steam  nozzle  carries  a 
conical  valve,  which  closes  the  passage  to  the  combining  cone,  and 
when  the  regulating  handle  is  turned  this  valve  lifts  and  allows 
steam  and  water  to  pass  into  the  combining  cone.  In  other  forms 
of  their  apparatus,  and  also  in  Messrs.  Davies  &  Metcalfe's,  the 
quantity  of  water  is  regulated  by  merely  pushing  the  steam  nozzle 
forwards,  or  withdrawing  it,  by  moving  the  regulating  handle,  the 
water  passage  being  decreased  or  increased  by  this. 

With  exhaust  steam  it  is  claimed  that  water  can  be  delivered  to 
the  boiler  up  to  a  temperature  of  190°  F. ;  while  with  the  addition  of 


BBBBBi 


PLATE  10A. — Evaporator  made  by  the 
Central  Engineering  Works,  Hartlepool. 


PLATE  10D. — Single  Cylinder  Verti- 
cal Engine,  made  by  Tangye. 


c6    Q^ 

H  § 
I  'fib 


[To  face  p.  176. 


BOILER   ACCESSORIES 


177 


live  steam,  as  explained,  it  may  be  introduced  at  any  temperature 
desired. 

The  injector  may  be  made  to  take  water  from  a  tank  at  a  higher 
level,  the  water  flowing  by  gravity  into  the  injector,  and  thence  being 
forced  into  the  boiler ;  or  it  may  lift  water  from  a  tank  or  any  supply 
at  a  lower  level,  and  then  force  it  into  the  boiler,  but  in  that  case  the 
quantity  of  water  the  injector  can  deliver  is  reduced.  Thus,  when 
the  water  has  to  be  lifted  6  feet,  the  quantity  the  injector  is  able  to 
deliver  is  reduced  about  10  per  cent. ;  with  a  lift  of  12  feet,  it  is 
reduced  25  per  cent. ;  and  with  18  feet,  35  per  cent. 

The  quantity  of  water  the  injector  can  deliver  depends  directly 
upon  the  pressure  of  steam  behind  it,  but  the  following  table,  given 
by  Messrs.  Babcock  &  Wilcox  for  their  live  steam  injector,  will  show 
the  matter  pretty  clearly.  The  injectors,  it  will  be  seen,  are  made  to 
deliver  from  122  gallons  per  hour  with  a  boiler  pressure  of  120  Ibs., 
up  to  nearly  12,000  gallons  per  hour  with  a  boiler  pressure  of  200  Ibs., 
the  quantity  that  can  be  delivered  increasing  with  the  boiler  pressure, 
but  not  in  proportion  to  it. 

TABLE   XVII. 

QUANTITIES  OF  WATEE  THAT  INJECTORS  WILL  DELIVER  AT  DIFFERENT  PRESSURES 


Pressure  of  steam. 

Size. 

Size  of  pipes 
and  fittings. 

120  pounds. 

140  pounds.       160  pounds. 

180  pounds. 

200  pounds. 

Maximum  delivery  in  gallons  per  hour. 

Inches. 

2i 

Inches. 
$ 

122 

131 

141 

149 

158 

3 

i 

196 

211 

227 

241 

257 

4 

1 

348 

376 

403 

426 

453 

5 

1 

545 

587 

630 

666 

703 

6 

H 

783 

846 

905 

958 

1,020 

7 

1| 

1067 

1152 

1,232 

1,304 

1,389 

8 

1J 

1393 

1505 

1,607 

1,705 

1,820 

9 

4 

1763 

1905 

2,037 

2,159 

2,302 

10 

2                  2177 

2352 

2,512 

2,738 

2,991 

11 

2                  2633 

2846 

3,041 

3,258 

3,507 

12 

2                  3136 

3387 

3,620 

3,840 

4,098 

13 

2J 

3680 

3975 

4,250 

4,506 

4,807 

14 

2* 

4267 

4610 

4,928 

5,226 

5,576 

15 

2* 

4900 

5292 

5,656 

5,998 

6,320 

16 

3 

5575 

6022 

6,435 

6,825 

7,283 

17 

3 

6291 

6798 

7,680 

7,728 

8,244 

18 

3 

7055 

7633 

8,148 

8,636 

9,208 

19 

3 

7861 

8492 

9,096 

9,792 

10,584 

20 

3 

8710 

9410 

10,048 

10,952 

11,964 

The  temperature  at  which  the  water  is  delivered  to  the  injector 


178     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

aftects  the  quantity  the  injector  will  force  into  the  boiler.  The 
higher  the  temperature  at  which  the  water  is  delivered  to  the  injector, 
the  smaller  the  quantity  the  injector  can  handle.  The  following 
table,  given  by  Messrs.  Holden  &  Brooke,  shows  the  effect  of  higher 
temperature  of  water  upon  the  delivery.  It  will  be  seen  that  with  a 
boiler  pressure  of  100  Ibs.  per  square  inch,  the  injector,  according  to 
their  experience,  ceases  to  work  reliably  when  the  feed  water  is 
delivered  to  the  injector  at  over  120°  F.  There  is  a  critical  tempera- 
ture with  every  boiler  pressure  at  which  the  injector  ceases  to  work 
reliably,  the  temperature  falling  as  the  pressure  rises. 

TABLE  XVIII. 
EFFECT  OF  HOT  FEED  WATER  ALONE  UPON  CAPACITY. 

Example  showing  the  diminution  in  capacity  of  injectors  caused  by  the  use  of  hot 
feed  water.  The  figures  refer  to  an  injector  fixed  non-lifting  and  working  with 
and  against  a  boiler-pressure  of  100  pounds  per  square  inch. 


Temperature 

of  feed  water 

entering  the 

50° 

60° 

70° 

80°    j    90° 

100° 

110° 

120° 

125°      130° 

injector.  De- 

grees Fahr. 

Percentage  of  ) 

diminution    > 

0 

1| 

3      !      5 

7* 

10J    j    18* 

19* 

24 

100 

delivery.         j 

| 

The  following  table,  given  by  Messrs.  Holden  &  Brooke,  shows 
the  temperatures  up  to  which  their  injectors  will  receive  feed  water. 


TABLE   XIX. 
CRITICAL  TEMPERATURES  OF  FEED  WATER,  WITH  DIFFERENT  PRESSURES. 


Boiler  pressure. 
Pounds. 
25  > 
30$  ' 
35 
80 
100 
150 
250 


Temperature  at  which  injector 
will  take  feed  water 
(fixed  non-lifting). 

150°  Fahrenheit 


150° 
135° 
125° 
105° 
80° 


Feed -Water  Regulators 

One  of  the  troubles  in  connection  with  boiler  plant  is  the  efficient 
control  of  the  feed.     If  the  feed  water  enters  the  boiler  in  too  great 


BOILER   ACCESSORIES  179 

quantity,  the  steam  pressure  must  go  down  ;  and,  on  the  other  hand, 
if  it  is  insufficient  in  quantity,  steam  cannot  be  maintained.  The 
flow  is  regulated  by  the  "  check  valve,"  worked  by  hand,  but  devices 
have  been  arranged  for  controlling  the  supply  automatically.  One 
of  these  shown  is  made  by  the  Williams  Gauge  Company  of  Pitts- 
burg,  U.S.A.  It  consists  practically  of  a  float,  carried  inside  a  vessel 
containing  water,  fixed  on  the  front  of  the  boiler,  and  in  which  the 
water  will  be  at  the  same  level  as  in  the  boiler.  It  is  practically  the 
water-gauge  of  the  boiler.  The  water-gauge  is  carried  on  its  front, 
and  the  gauge  cocks  at  the  side.  It  is  arranged  that  as  the  level  of 
the  water  rises  and  falls,  the  float  rises  and  falls  with  it,  and  closes 
or  opens  the  steam  admission  valve  that  is  working  the  feed  supply. 
It  is  also  arranged  that,  should  the  pump  fail,  the  feed- water  regulator 
sounds  a  whistle  until  attention  is  called ;  and  should  the  regulator 
itself  fail,  an  alarm  is  sounded  when  the  water  is  at  the  maximum 
height  it  is  designed  to  work  with. 


Purifying  the  Feed  Water 

From  what  has  been  said  in  previous  portions  of  this  and  the 
first  chapter,  it  will  be  understood  that  the  purity  of  the  water  that 
is  employed  in  boilers  for  raising  steam  is  of  enormous  importance. 
As  explained  in  the  first  chapter,  water  has  the  important,  and,  so 
far  as  boiler  work  is  concerned,  the  troublesome  property  of  not  only 
dissolving  portions  of  the  rocks,  earths,  etc.,  over  and  through  which 
it  flows,  but  also  of  carrying  minute  portions  of  them  in  mechanical 
suspension.  Every  one  is  familiar  with  the  worn  surfaces  of  rocks 
in  river  beds.  Part  of  the  wearing  is  due  to  solution  of  the  substances 
of  which  the  rocks  are  composed,  and  part  again  is  often  due  to 
attrition,  to  the  wearing  away  and  carrying  off  of  minute  particles 
of  the  substances  in  the  same  chemical  condition  as  they  existed 
when  forming  portions  of  the  rocks.  In  addition  to  this,  all  water 
supplies  that  are  available  for  boiler  feed  are  liable  to  the  presence 
of  organic  matter.  The  water  supply  of  towns  is  obliged  to  be 
filtered  from  this  cause,  and  water-works  engineers  know  that  at 
certain  times  of  the  year,  such  as  in  spring  and  early  summer,  and 
again  in  autumn,  large  quantities  of  vegetable  matter  find  their  way 
into  the  springs  and  rivers  from  which  water  supplies  are  taken,  and 
a  considerable  quantity  remains,  even  after  filtration.  Prof.  Thurston 
estimates  that  from  water  that  is  considered  to  be  very  pure,  a  100 
H.P.  boiler  will  receive  as  much  as  90  Ibs.  of  foreign  matter  per 
hour ;  while  from  other  sources  not  as  pure,  as  much  as  1  ton  per 
hour  is  sometimes  carried  in,  and  has  to  be  got  rid  of. 


i8o    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

In  addition  to  the  matter  held  in  suspension,  as  described,  the 
water  has  also  salts  of  calcium  and  magnesium,  which  go  to  give  it 
what  is  termed  "  hardness." 

The  term  "hard  water"  is  familiar  as  applied  to  water  that  does 
not  lather  with  soap  in  the  ordinary  way,  and  the  relative  degree  of 
hardness  of  different  kinds  of  water  is  measured  by  the  quantity 
of  soap  which  it  absorbs  uselessly  before  it  commences  its  work 
of  cleansing,  etc.  The  hardness  of  water  is  measured  in  degrees, 
though  the  measurement  is  a  very  arbitrary  one,  and  the  degrees  are 
to  be  understood  as  something  quite  different  from  those  used  in 
connection  with  circles,  etc.  A  degree  of  hardness  in  water  means 
that  a  gallon  of  the  water  contains  sufficient  salts  in  solution  to 
decompose  as  much  soap  as  would  be  decomposed  by  one  grain  of 
carbonate  of  lime  (chalk).  Thus  water  is  said  to  have  10°  or  15°  or 
20°  of  hardness,  as  the  case  may  be,  when  it  contains  the  quantities 
of  salts  per  gallon  that  will  decompose  the  same  quantities  of  soap 
as  10,  15,  or  20  grains  of  chalk. 

Hardness  of  water  again  is  divided  into  temporary  hardness  and 
permanent  hardness.  Temporary  hardness  is  caused  principally  by 
the  presence  of  the  bi- carbonates  of  lime  and  magnesia.  By  the 
bi-carbonate  is  meant  the  salt  which  contains  two  chemical  equiva- 
lents of  carbonic  acid  to  one  of  lime  or  magnesia,  the  carbonate  con- 
taining only  one  chemical  equivalent  of  carbonic  acid  combined  with 
one  chemical  equivalent  of  lime  or  magnesia.  Temporary  hardness 
is  got  rid  of  by  raising  the  temperature  of  the  water  in  which  the 
bi-carbonates  are  dissolved  to  320°  F.,  or  by  the  addition  of  lime,  the 
lime  combining  with  the  second  equivalent  of  carbonic  acid  and 
forming  carbonate.  At  the  temperature  mentioned,  one  of  the 
equivalents  of  carbonic  acid  is  driven  off  as  a  gas,  leaving  the  remain- 
ing salt  in  the  form  of  the  carbonate,  which  is  not  soluble  in  water, 
and  which  is  therefore  deposited,  if  suitable  means  are  provided  for 
it,  in  the  vessel  in  which  the  operation  takes  place.  Permanent 
hardness  is  caused  by  the  presence  of  the  chlorides  and  sulphates  of 
lime  and  magnesia,  and  some  of  these  are  not  driven  off  by  raising 
the  temperature,  but  are  usually  got  rid  of  by  chemical  action.  If 
the  chlorides  and  sulphates  and  carbonates  are  not  removed  from 
the  water  before  it  enters  the  boiler,  they  are  deposited  upon  the 
water  side  of  the  heating  surfaces,  the  outsides  of  the  flues,  furnaces, 
etc.,  in  the  Lancashire  boilers,  and  the  inside  of  the  boiler  shell,  and 
on  the  inside  of  the  tubes  of  water-tube  boilers,  with  the  result  that 
a  scale  is  built  up,  as  already  explained,  which  resists  the  passage  of 
heat  through  it. 

The  sulphates  and  chlorides  are  removed  by  the  addition  of 
carbonate  of  soda,  a  carbonate  of  lime  being  formed,  which,  as 
explained,  is  deposited,  and  a  sulphate  of  soda  which  does  not  form 


BOILER   ACCESSORIES  181 

a  scale.     There  are  several  forms  of  what  are  called  water  softeners, 
the  principal  of  which  are  described  below. 


Other  Scale=forming  Substances 

In  addition  to  the  organic  and  other  matters  held  in  suspension, 
and  to  the  salts  held  in  solution,  there  are  other  matters  which  have 
a  very  serious  effect  upon  the  working  of  the  boiler,  and  upon  the 
formation  of  scale.  As  will  be  seen  later,  when  describing  engines 
and  their  working,  it  is  necessary  to  employ  oil  for  the  lubrication 
of  reciprocating  engine  cylinders,  and  a  small  quantity  of  the  oil  is 
continually  carried  over  with  the  exhaust  steam  to  the  condenser 
and  to  the  feed-water  heater,  where  these  are  employed,  with  the 
result  that,  unless  means  are  taken  to  prevent  it,  a  very  difficult 
matter  if  the  condensed  water  is  used  for  feeding  the  boiler,  a  portion 
of  the  oil  remains  in  the  feed  water  and  works  its  way  back  into  the 
boiler.  It  has  been  found  that  a  very  thin  layer  of  oil  on  the  surface 
of  the  furnace  crown,  for  instance,  offers  such  a  high  resistance  to  the 
passage  of  heat  from  the  furnace  gases  to  the  water  above  them,  that 
the  crowns  of  the  furnaces  often  become  very  dangerously  heated 
indeed,  the  heat  not  being  able  to  escape  to  the  water,  and  serious 
trouble  sometimes  resulting.  In  addition  to  this,  the  minute  quantities 
of  oil  combine  with  the  sulphates  and  carbonates,  and  sometimes  with 
the  organic  matter,  if  it  is  allowed  to  remain  in  the  water,  the  scale  so 
formed  being  of  great  tenacity  and  hardness,  and  giving  considerable 
trouble  to  remove. 

Another  source  of  trouble  in  boilers  is  electrolytic  action.  The 
different  parts  of  the  boiler,  it  will  be  remembered,  are  subject  to 
the  action  of  the  hot  gases  at  different  temperatures,  and  consequently 
the  metal  portions  of  the  boilers  at  these  points  are  themselves  at 
different  temperatures,  and  this  leads  to  the  formation  of  a  galvanic 
battery,  there  being  a  difference  of  electrical  pressure  between  the 
iron  or  steel  at  the  higher  temperature  and  that  at  the  lower 
temperature.  This,  together  with  the  presence  of  water,  particularly 
when  the  water  contains  salts  in  solution,  leads  to  the  passage  of 
electric  currents  from  one  part  of  the  boiler  to  the  other,  through 
the  water,  and  to  the  eating  away  of  the  boiler  at  those  portions, 
generally  the  hotter  portions,  from  which  the  current  sets  out. 


Methods  of  Removing  Foreign  Bodies,  etc. 

The  case  of  the  feed-water  heater  has  been  mentioned  above,  in 
which  provision  is  made  for  removing  the  foreign  bodies  that  are 


1 82     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

thrown  down  into  the  chamber  provided  for  them,  also  in  describing 
several  of  the  boilers,  mud  drums  and  scum  cocks  were  also  mentioned. 
The  mud  drums  are  for  the  reception  of  all  the  matter  held  in  sus- 
pension, and  all  that  can  be  arranged  to  be  held  in  suspension,  by 
the  action  of  the  boiler,  and  are  fixed  at  the  lowest  point,  and  often 
well  below  the  boiler,  in  order  that  all  of  these  substances  may 
gravitate  there.  In  Lancashire  boilers  the  lower  part  of  the  boiler 
below  the  furnace  is  the  spot  to  which  these  substances  usually 
gravitate.  Scum  cocks  are  fitted  to  the  lower  part  of  the  front  of 
the  Lancashire  boiler,  and  to  the  lower  part  of  the  mud  drums  of 
water-tube  and  other  boilers.  When  the  scum  cock  is  opened,  the 
pressure  of  steam  in  the  boiler,  which,  it  will  be  remembered,  is 
communicated  by  the  law  governing  pressures  in  fluids,  to  all  parts 
of  the  fluids  in  the  boiler,  forces  the  semi-solid  substances — the 
scum,  in  fact — out  through  the  scum  cock  into  receptacles  provided 
for  it. 


Water  Softeners 

Water  softeners  are  practically  constructed  all  on  the  same  lines, 
with  the  usual  variations  by  different  inventors.  The  common 
practice  in  all  of  them  is  to  add  to  the  water  to  be  softened  a  definite 
quantity  of  hydrate  of  lime,  and  carbonate  of  soda.  Success  in 
removing  the  substances  which  make  water  hard,  depends  very 
largely  upon  the  reagents,  as  they  are  called,  the  lime  and  carbonate 
of  soda  being  added  in  proper  proportions,  and  therefore  the  manu- 
facturers of  all  water-softening  apparatus  ask,  as  a  preliminary,  that 
the  water  shall  be  submitted  to  them  for  analysis,  so  that  they  may 
know  the  proper  proportion  of  the  reagents  to  add.  If  too  little  of 
the  reagents  are  added  to  the  water  to  be  softened,  it  will  be  evident 
that  a  portion  of  the  substances  causing  the  hardness  will  remain ; 
and,  further,  there  is  always  the  possibility  of  chemical  action  taking 
place  between  the  new  substances  formed  and  the  remainder  of  the 
sulphates  or  chlorides,  in  the  presence  of  heat,  and  in  the  presence 
of  the  oil  and  organic  matter  that  is  sometimes  found  there.  On  the 
other  hand,  if  too  much  of  the  reagent  is  added,  there  will  be  a 
surplus  of  it  in  the  water,  and  in  some  cases  this  will  have  a  dele- 
terious effect.  In  all  of  the  apparatus  made,  therefore,  one  portion 
is  devoted  to  measuring  definite  quantities  of  the  reagents,  against 
definite  quantities  of  the  water  to  be  softened.  A  second  equally 
important  requisite  in  the  water  softener  is  the  thorough  mixing 
of  the  reagents  with  the  water  to  be  softened.  It  will  be  quite 
evident  to  any  one  who  has  observed  the  action  of  the  solution  of 
different  substances  in  water,  that  time  is  always  necessary  for 


BOILER   ACCESSORIES  183 

complete  solution  to  be  accomplished,  though  the  time  may  be 
considerably  lessened  by  stirring,  and  other  methods ;  and,  con- 
sequently, in  all  of  the  apparatus  some  form  of  stirrer  or  mixer 
occupies  a  prominent  position. 

The  next  important  part  of  the  apparatus  is  that  in  which  the 
separation  of  the  new  substances  that  have  been  formed,  and  that 
are  purposely  made  insoluble  in  the  water,  takes  place. 

In  nearly  all  of  the  apparatus  a  filter  forms  an  important  feature 
in  the  last  part  of  the  operation.  The  filter  is  usually  formed  of 
wood  wool. 

In  some  of  the  water-softening  apparatus,  steam  is  used  to  heat 
the  water,  and  to  throw  off  the  carbonic  acid,  as  explained  on  p.  180, 
while  others  claim  that  the  whole  process  is  carried  on  without  the 
addition  of  heat.  In  one  apparatus,  the  Archbutt-Deely,  made 
by  Messrs.  Mather  and  Platt,  the  water  is  also  charged  to  a  small 
extent  with  carbonic  acid,  after  it  has  been  softened.  In  one 
apparatus  also,  the  Harris-Anderson,  which  is  intended  to  remove 
the  oil  from  the  water,  as  well  as  to  soften  it,  sulphate  of  alumina 
and  carbonate  of  soda  are  added  to  the  water  in  place  of  lime  and 
carbonate  of  soda. 


The  Archbutt-Deeley  Water  Softener 

The  Archbutt-Deely  apparatus,  which  has  been  worked  out  by 
the  engineers  of  the  Midland  Eailway,  is  intended  mainly  for  dealing 
with  large  quantities  of  water.  It  consists  of  two  tanks  which  are 
used  alternately,  the  water  to  be  softened  being  treated  in  one  tank, 
while  the  softened  water  is  being  drawn  off  from  the  other.  In  the 
lower  part  of  the  tanks  are  two  sets  of  steam  pipes,  and  above 
the  main  tanks  is  a  small  tank  for  chemicals,  in  which  definite 
quantities  of  quicklime  and  carbonate  of  soda  are  boiled  by  means 
of  live  steam,  the  proportion  of  the  chemicals  being  regulated 
according  to  the  hardness  of  the  water.  The  tank  to  be  operated 
upon  is  filled  by  means  of  a  pump,  and  then  by  the  aid  of  steam 
the  prepared  chemical  solution  is  forced  into  the  water,  a  current 
being  set  up  in  the  water  in  the  tank,  and  the  chemical  solution 
being  gradually  drawn  down  through  a  pipe  provided  for  it,  from  the 
tank  in  which  it  was  prepared,  and  being  drawn  into  the  circulating 
current  in  the  main  water  tank,  and  gradually  mixed  with  the  water 
to  be  softened.  One  special  feature  of  the  Archbutt-Deely  apparatus 
is  the  method  by  which  precipitation  of  the  foreign  substances  is 
obtained.  The  mud,  as  it  is  called,  from  previous  bodies  of  water  that 
have  been  treated,  is  allowed  to  remain  on  the  bottom  of  the  tank, 
and  when  the  chemical  solution  has  thoroughly  mixed  with  the 


1 84    STEAM   BOILERS,  ENGINES,  AND   TURBINES 

water,  the  mud  precipitate  is  stirred  up  by  means  of  air  bubbles, 
forced  from  the  lower  row  of  pipes  in  the  tank  by  the  aid  of  steam. 
The  disturbance  of  the  old  precipitate  is  stated  to  greatly  accelerate 
the  precipitation  of  the  new  matter  that  has  been  thrown  out  of  the 
hard  water  by  the  chemical  reagents,  and  that  is  in  a  very  finely 
divided  state,  and  will  take  a  long  time  to  settle  unless  means  are 
taken  to  assist  it.  When  the  old  precipitate,  which  consists  of  coarse 
particles,  is  stirred  up,  the  fine  particles  of  the  new  precipitate 
attach  themselves  to  the  coarse  particles,  and  the  whole  subsides 
to  the  bottom  by  gravity,  in  the  usual  way.  After  the  air  has  been 
operating  for  a  few  minutes,  the  time  varying  with  different  waters, 
the  steam  is  turned  off,  and  the  precipitate  is  allowed  to  settle. 
It  is  found  that  the  whole  will  settle  to  the  bottom,  and  that  the 
water,  even  to  a  depth  of  6  feet  from  the  surface,  is  clear  and  pure, 
and  does  not  contain  more  than  one  grain  of  suspended  matter  per 
gallon.  After  the  water  has  settled,  the  clear  portion  is  drawn  off 
and  carbonated  by  means  of  fuel  gas,  from  a  coke  stove,  the  gas 
being  blown  into  the  water  by  the  aid  of  a  steam  nozzle,  and  being 
caused  to  mix  with  the  water  by  means  of  baffles.  Messrs.  Archbutt 
&  Deely  state  that  uncarbonated  softened  water  is  liable  to  form  a 
deposit  in  pipes,  and  especially  in  the  feed  apparatus  of  steam  boilers, 
and  it  is  for  this  reason  they  adopt  the  carbonating  process.  The 
mud  is  removed  from  the  tanks  from  time  to  time,  through  mud 
doors,  or  by  steam  lifters. 


The  Criton  Water  Softener 

In  the  Criton  water  softener,  made  by  the  Pulsometer  Company, 
no  heat  is  employed.  The  apparatus  is  shown  in  section  in  Fig.  68. 
It  will  be  noticed  that  there  is  a  tank  for  lime  water  on  the  left, 
with  a  ball  cock  for  filling  it,  and  an  overflow  trough.  Also  that 
there  is  a  tank  above,  marked  syphon  tank,  and  alongside  of  it 
another  marked  soda  tank.  The  pipe  bringing  the  hard  water  is  seen 
dipping  into  the  syphon  tank,  and  a  float,  dipping  into  the  syphon 
tank  also,  controlling  by  means  of  a  system  of  levers  a  plunger, 
called  in  the  drawing  a  displacer,  in  another  small  vessel  below  the 
soda  tank.  It  will  be  noticed  also  that  there  is  a  plunger,  also 
called  a  displacer,  in  the  upper  portion  of  the  lime-water  tank.  On 
the  right  of  the  drawing  will  be  noticed  a  larger  vessel,  marked 
settling  tank,  with  a  vessel  at  the  top,  open  above,  and  having  a  pipe 
leading  from  the  bottom  to  the  bottom  of  the  settling  tank.  Pipes 
will  be  noticed  also  leading  from  below  the  syphon  tank,  and  from 
the  small  tank  at  the  side  of  the  soda  tank,  into  the  vessel  above  the 


BOILER   ACCESSORIES 


185 


settling  tank,  which  is  called  the  mixer.  The  operation  of  the  appa- 
ratus is  as  follows.  The  syphon  tank  is  filled  from  the  water  inlet, 
the  lime-water  tank  having  also  been  filled  from  the  same  source,  and 
having  a  quantity  of  lime 
dissolved  in  it.  As  the 
level  of  the  water  in  the 
syphon  tank  rises,  it  raises 
the  float  shown,  this  de- 
pressing the  plunger  in  the 
small  tank  by  the  side  of 
the  soda  tank,  and  causing 
a  quantity  of  the  soda 
solution,  which  has  been 
made  in  the  soda  tank,  to 
pass  into  the  mixer.  At 
the  same  time  the  plunger 
in  the  lime-water  tank  is 
pushed  downwards,  causing 
a  certain  quantity  of  lime 
water  to  flow  over  the 
trough  shown  into  the 
mixer,  the  hard  water  from 
the  syphon  tank  flowing 
also  through  the  pipe  shown, 
the  whole  mixing  together, 
and  passing  downwards 
through  the  pipe  in  the 
settling  tank  to  the  bottom. 
A  large  portion  of  the  im- 
purities that  have  been 
displaced  by  the  chemical 
action  are  claimed  to  settle 
on  the  bottom  of  the  set- 
tling tank,  and  are  removed 
from  time  to  time  through 
the  tap  shown  on  the  right. 
The  water  rises  in  the 
settling  tank,  passes  out 


FIG.  68. — Section  of  Criton  Water  Softener.  The 
Syphon  Tank  which  receives  the  Water  to  be 
softened  is  seen  at  the  top,  where  the  Soda 
Tank  is  also  fixed,  the  Lime-water  Tank  and 
the  Filter  and  Settling  Tank  being  below. 


through  the  pipe  shown  at 

the  top,  into  the  filter,  and 

down  through  the  filter  to  the  outlet.     The  filter  is  arranged  to  be 

cleaned,  without  removal,  by  a  reverse  current  of  water  through  the 

valves  shown. 


1 86    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Reisert  Water  Softener 

In  this  apparatus,  which  is  made  by  Messrs.  Koyle  of  Irlara, 
there  is  the  usual  cylindrical  main  chamber,  with  a  tank  above,  and 
a  conical- shaped  vessel  on  the  right.  The  water  to  be  softened  enters 
the  tank  at  the  top,  which  is  divided  into  three  chambers,  one  for 
lime  slaking,  one  for  making  a  soda  solution,  and  a  third  for  the 
water  by  itself.  The  conical-shaped  chamber  is  called  the  lime 
saturator,  and  its  office  is  to  prepare  the  solution  of  lime  water 
to  be  employed  in  the  softening  process.  Water  enters  the  lime 
saturator  from  the  middle  chamber  of  the  water  tank,  through  a 
micrometer  valve  marked,  and  it  passes  directly  down  a  central  pipe, 
to  the  bottom  of  the  chamber,  the  slaked  lime  being  delivered  some 
little  distance  from  the  bottom  of  the  chamber,  by  a  pipe  and  funnel 
from  the  lime  chamber.  The  water  delivered  from  the  bottom  of 
the  central  pipe  passes  upwards,  its  velocity  gradually  decreasing  as 
the  diameter  of  the  chamber  increases,  and  it  is  claimed  that  by 
this  method  the  water  becomes  thoroughly  saturated  with  lime, 
any  undissolved  lime  particles  falling  to  the  bottom.  On  the  left 
there  is  a  similar  chamber,  but  of  rectangular  shape,  into  which 
the  solution  of  soda  is  delivered  by  a  pipe  and  cock,  water  passing 
into  another  chamber  at  the  same  time,  through  another  micrometer 
valve  in  the  central  water  chamber,  and  the  pipe  attached  to  it. 
Small  pipes  lead  from  the  top  of  the  lime  saturator,  and  from  the 
soda  solution  chamber  to  a  distributing  tank,  which  is  held  inside 
of  the  main  cylinder,  the  water  to  be  softened  also  passing  to  the 
same  chamber  through  the  micrometer  valve,  in  the  central  portion 
of  the  tank  above,  and  the  pipe  attached  to  it.  The  water  to  be 
softened  and  the  solutions  of  lime  and  soda  that  are  to  soften  it 
are  delivered  in  definite  quantities  into  the  middle  chamber  of  the 
water  tank,  passing  down  through  it,  and  up  through  the  body  of 
the  liquid  which  fills  the  main  cylindrical  chamber,  and  from  there 
the  mixed  water  passes  down  a  central  pipe  to  the  under  side  of  the 
filter  at  the  bottom.  After  passing  through  the  filter  the  water  is 
delivered  to  a  tank  on  the  left.  There  is  in  addition,  a  syphon  tube, 
on  the  right,  connected  with  the  tank  on  the  left  by  the  small 
pipe,  and  one  of  the  features  claimed  in  connection  with  the  Eeisert 
apparatus  is,  the  automatic  cleaning  of  the  filter.  It  will  be  under- 
stood that  a  certain  amount  of  precipitation  takes  place  in  the  lower 
part  of  the  main  cylinder,  and  that  any  precipitates  remaining  are 
absorbed  by  the  filter,  whose  pores  gradually  become  filled  up.  As 
the  passage  of  the  water  through  the  filter  is  checked,  as  the  pores 
become  filled,  the  liquid  rises,  and  when  the  resistance  offered  by 
the  filter  reaches  a  certain  figure,  a  syphon  is  formed,  reversing  the 


BOILER  ACCESSORIES 


187 


direction  of  the  water  through  the  filter,  cleansing   the  filter,  and 
carrying  off  the  precipitate  by  a  cock  provided  for  it. 

For  locomotive  and  tubular  boilers,  in  the  Eeisert  water  softening 
apparatus,  lime  is  used  in  conjunction  with  carbonate  of  barium. 


The  Bruun  Lowener  Water  Softener 


This  apparatus  is  made  in  this  country  by  Messrs.  Lassen  and 
Hjort.  It  is  shown  in  Fig  69.  The  water  is  led  into  one  of  two 
chambers  of  the  oscil- 
lating receiver  C,  which 
is  pivoted  over  the  vessel 
B  in  which  the  princi- 
pal action  takes  place. 
Above  the  oscillator  is  a 
semi-  cylindrical  tank,  in 
which  the  reagents  are 
held,  consisting  of  lime 
milk  and  carbonate  of 
soda.  The  makers  state 
that  the  lime  milk  that 
is  used  has  a  strength 
of  10  per  cent.,  and  that 
it  is  made  from  freshly 
burned  lime.  The  chem- 
icals are  kept  in  constant 
motion  within  the  semi- 
cylindrical  vessel  by 
means  of  the  agitator 
shown.  At  the  bottom 
of  the  vessel  carrying 
the  chemicals  is  a  valve, 
which  is  opened  by  a 
system  of  levers  at  every 
tujcn  of  the  oscillator. 
When  one  of  the  vessels 
of  the  oscillator  is  full, 
it  tips  over,  and  empties 
its  contents  into  the 

^•u   ™-k        -D    i™ 
mixing   Chamber    B    be- 

low,    and    at    the    same 

time  a  definite  quantity 
of  the   lime   milk   and 


FIG.  69.  —  Vertical  type  of  Bruun  Lowener  Water 
Softener,  with  Parts  of  the  Containing  Vessel  cut 
away  to  show  the  interior,  c  is  the  Oscillator  ; 

b  the  Mixer  ;  '  is  the  Filter,  at  the  top. 


carbonate  of  soda,  thoroughly  mixed  together,  are  delivered  to  the 
mixing  chamber.     The  water  and  the  reagents  are  kept  in  motion 


1 88     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

within  the  mixing  chamber  by  means  of  a  plate  fixed  to  the  bottom 
of  the  oscillator.  From  the  mixing  chamber  the  water  passes  to  a 
heating  chamber,  and  which  is  provided  with  a  steam  nozzle,  the 
temperature  of  the  water  being  raised  to  130°  F.  Some  of  the  foreign 
matters  are  precipitated  in  the  heating  chamber.  From  the  heating 
chamber  the  water  passes  into  the  settling  tank,  where  precipitation 
of  the  foreign  substances  takes  place,  and  from  thence  it  passes  up 
through  the  filter  I,  which  is  made  of  wood  wool,  and  thence  to  the 
boiler  or  feed  pump,  etc. 


Quttmann  Water  Softener 

In  the  Guttmann  apparatus,  which  is  made  by  Messrs.  Babcock 
and  Wilcox,  there  is  a  chemical  tank  at  the  top  of  the  apparatus, 
into  which  the  quantity  of  the  usual  chemicals,  sufficient  for  the 
day's  work,  is  put,  the  tank  then  being  filled  with  water.  Below 
the  chemical  tank  stands  the  mixing  or  reaction  tank,  into  which 
the  water  to  be  softened  is  carried,  a  certain  quantity  of  the  solution 
of  the  reagents  also  passing  into  it  from  the  chemical  tank,  the 
admission  of  water  and  reagents  being  controlled  by  valves.  The 
water  and  solution  in  the  reaction  tank  are  raised  to  boiling-point 
by  the  aid  of  steam  delivered  to  the  tank  by  means  of  injectors,  the 
whole  being  thoroughly  agitated  at  the  same  time.  The  water  flows 
from  the  reaction  tank  into  the  filter  tank,  which  is  arranged 
in  steps,  the  bottom  of  each  step  forming  a  filter,  and  the  water 
being  caused  to  take  a  zigzag  course  by  the  division  plates  being 
arranged  to  leave  spaces  for  the  water  alternately  at  the  top  and 
bottom.  A  certain  amount  of  precipitation  takes  place  as  usual  in 
the  reaction  tank,  and  the  remainder  is  carried  out  in  the  filter 
tank,  by  successive  steps,  as  explained.  From  the  filter  tank  the 
water  passes  into  the  storage  tank,  where  it  should  be  ready  for  use. 


Doulton's  Water  Softener 

The  special  feature  of  Messrs.  Doulton's  apparatus  is  the  arrange- 
ment for  mixing  the  chemicals  with  the  water  to  be  softened.  This 
portion  of  the  apparatus  is  shown  in  Fig.  70.  The  hard  water  is  led 
in  through  the  pipe  at  the  top  of  the  tank  on  the  left,  into  the 
tank  shown,  which  contains  a  float  W,  which  by  means  of  the  lever 
L,  and  the  cocks  F  and  N,  control  the  supply  of  the  chemicals  from 
the  tank  Y  on  the  right.  When  the  tank  G  on  the  left  has  been 
filled  to  a  certain  height,  and  the  float  W  has  thence  been  raised  to 
a  certain  height,  the  lever  L  opens  the  cocks  in  the  pipe  leading 


BOILER   ACCESSORIES  189 

from  the  tank  Y,  and  a  certain  definite  quantity  of  the  reagents  pass 
into  the  mixing  chamber,  shown  between  the  two  tanks.  At  the 
same  time  the  hard  water  from  the  tank  G  is  discharged  through 
the  shoot  Q  into  the  mixing  chamber,  where  it  is  given  a  whirling 
motion,  this  motion  causing  the  required  mixing  of  the  reagents  with 


FIG.  70. — Mixing  portion  of  Doulton's  Water  Softener.    Y  is  the  Chemical  Tank ; 
G  the  Tank  receiving  the  Water  to  be  softened. 

the  water.  When  mixing  has  been  effected,  the  water  and  reagents 
pass  through  the  funnel  V,  down  to  the  bottom  of  a  settling  tank,  at 
the  bottom  of  which  precipitation  takes  place,  the  water  then  rising 
through  a  filter  at  the  top  and  passing  on. 


The  Kennicott  Water  Softener 

In  the  Kennicott  water  softener  there  is  a  cylindrical  steel  tank, 
having  a  water  wheel  at  the  top,  over  which  the  water  to  be  softened 
passes,  the  power  delivered  by  the  water  being  made  use  of  to  raise 
the  reagents  to  the  top  of  the  tank.  Tanks  containing  the  reagents 
are  also  fixed  above  the  main  tank.  The  reagents  pass  into  the  water 
wheel,  with  the  water  to  be  softened,  thence  down  through  a  pipe 
in  the  centre  of  the  apparatus,  to  the  bottom  of  the  chamber,  from 
which  they  turn  and  rise  through  a  series  of  inclined  perforated  baffle 
plates,  any  precipitate  which  has  not  been  left  at  the  bottom  of  the 
tank  being  caught  by  these  plates,  from  which  it  falls  off  to  the 
bottom  of  the  tank.  The  water  finally  passes  through  a  wood-fibre 
filter  at  the  top  of  the  tank. 


190     STEAM   BOILERS,   ENGINES,   AND    TURBINES 


The  Desrumaux  Water  Softener 

In  this  apparatus  there  are  two  tanks,  one  called  the  saturator, 
in  which  a  portion  of  the  water  to  be  softened  is  saturated  with  lime, 


FIG  71  —Section  of  the  Desrumaux  Water  Softener.  The  Saturator  is  shown  on 
'the  left,  with  the  Water-wheel  Stirrer.  The  Water  Wheel  at  the  top  of  the 
Main  Chamber  will  be  noted,  also  the  Spiral  Baffle  Plates. 

a    revolving   wheel   ensuring   that  the   mixing    is   complete.      The 
remainder  of  the  water  to  be  softened  passes  over  the  water  wheel, 


BOILER   ACCESSORIES  191 

the  power  delivered  to  the  wheel  being  employed  to  drive  the  stirrer 
in  the  saturator.  The  water  from  the  saturator  flows  into  the  centre 
of  the  main  chamber,  after  it  has  been  thoroughly  saturated,  and  there 
meets  the  water  to  be  softened  and  a  certain  quantity  of  a  solution 
of  soda,  from  a  rectangular  tank  above.  The  water  and  the  reagents 
pass  through  a  central  chamber  or  tube,  to  the  bottom  of  the  main 
tank,  where  precipitation  takes  place  as  usual,  the  water  then  rises 
to  the  top,  around  spiral  baffle  plates,  which  arrest  any  precipitate 
that  has  not  been  left  at  the  bottom,  the  matter  so  caught  finding  its 
way  to  the  bottom  of  the  main  tank.  At  the  top  of  the  main  tank 
the  water  passes  through  a  filter  in  the  usual  way. 


The  Arthur  Koppel  Water  Softener 

In  this  apparatus  the  precipitating  tank  may  be  either  cylindrical, 
rectangular,  or  any  convenient  shape.  The  chemical  tank  above  the 
precipitating  tank  may  also  be  cylindrical  or  rectangular.  One  of  the 
special  features  of  the  apparatus  is  the  arrangement  for  delivering 
the  required  quantity  of  each  reagent  to  the  water  to  be  softened.  It 
is  accomplished  by  bucket  conveyors.  There  is  a  tank  for  each  of  the 
reagents,  and  a  bucket  conveyor  dipping  into  each,  and  both  conveyors 
are  worked  by  oscillating  apparatus.  The  oscillating  vessel  is  on  some- 
what similar  lines  to  some  of  those  that  have  been  already  described. 
It  has  two  compartments,  and  the  water  that  is  to  be  softened  flows 
into  one  of  them,  tips  it ;  over  when  full,  allowing  the  water  that  has 
been  poured  into  it  to  pass  down  to  the  mixing  chamber,  while  the 
other  half  of  the  apparatus  comes  under  the  water  pipe.  The  oscil- 
lation of  the  tipples  is  made  to  work  the  elevators  bringing  the  re- 
agents by  means  of  a  ratchet  wheel  and  pawl.  The  quantity  of  the 
reagent  carried  upwards  by  the  bucket  of  the  conveyor,  is  tipped  over 
at  the  top  into  a  small  chamber,  from  which  it  flows  down  through  a 
pipe  into  the  mixing  chamber.  There  is  a  novel  form  of  steam  heating 
apparatus  in  the  chamber  into  which  the  water  is  tipped  from  the 
oscillator,  consisting  of  a  number  of  plates  over  which  the  water  flows, 
it  being  arranged  that  the  water  is  obliged  to  #o^  over  the  length  of 
each  plate  in  succession,  and  the  plates  are  heated  by  a  steam  jet 
passing  up  from  an  exhaust  steam  pipe,  the  steam  passing  up  over  the 
under  surfaces  of  the  plates,  from  plate  to  plate,  in  the  opposite 
direction  to  that  in  which  the  water  is  flowing,  the  water  thus  being 
heated  as  it  passes  over  them.  From  the  heating  chamber  the  water 
passes  down  through  a  pipe  into  the  mixing  chamber,  where  it  is 
further  heated  by  live  steam,  and  agitated  by  a  blast  of  air.  The 
complete  lower  chamber  is  divided  into  three  chambers,  the  division 
being  in  the  form  of  an  inverted  Y,  and  the  water  flows  down  round 


1 92     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  ends  of  the  division  plates,  and  then  up  through  the  filters  and 
out  to  the  feed  pipe,  the  foreign  matters  depositing  at  the  different 
points,  and  finally  settling  down  to  the  bottom  of  the  tank,  and  being 
removed  by  opening  a  valve  at  the  bottom. 


Harris=Anderson  Water  Softener 

In  the  Harris- Anderson  apparatus,  carbonate  of  soda  and  lime  are 
sometimes  used  in  conjunction,  as  in  other  apparatus,  and  sometimes 
lime  is  used  alone.  In  the  apparatus  employing  carbonate  of  soda, 
the  mixing  of  the  reagents  is  carried  out  by  special  apparatus,  quite 
different  to  any  of  those  that  have  been  described.  0'5  per  cent,  by 
volume  of  the  reagents  are  always  supplied  to  the  water  to  be  softened, 
no  matter  what  its  composition  may  be,  and  for  this  purpose  a  special 
apparatus,  known  as  a  distributor,  is  employed,  in  which  two  com- 
partments receive  J  per  cent,  of  the  total  flow,  and  two  others  49J 
per  cent.  The  proportion  of  the  water  received  in  the  J  per  cent! 
compartments,  is  taken  to  an  apparatus  called  the  solutioner,  con- 
sisting of  four  cylinders,  one  inside  the  other,  with  a  wire  gauze 
cage  fixed  in  the  top  of  the  inner  cylinder.  The  cylinders  are  so 
arranged  that  the  water  to  be  softened  circulates  in  the  annular 
spaces  between  them,  taking  up  the  reagent  in  the  wire  gauze  cylinder 
on  its  way,  and  they  are  further  arranged  so  that  their  position  can 
be  altered  at  will,  so  that  the  speed  of  flow  can  be  changed.  Follow- 
ing the  distributor  and  the  apparatus  for  mixing  the  solutions  of  the 
reagents,  comes  that  for  mixing  the  water  with  the  solutions  of  the 
reagents.  For  this  purpose  three  pairs  of  concentric  tubes  are  pro- 
vided,, one  for  each  half  of  the  water  and  the  solution  of  reagents, 
and  the  third  for  the  two  halves  of  the  water  and  reagents  together. 
One  half  of  the  water  and  the  one  half  of  the  prepared  solution  of 
reagents  is  passed  down  the  centre  of  one  set  of  tubes,  and  up  through 
the  annular  space  between  them,  the  two  streams  from  the  two  halves 
then  join,  and  pass  down  the  central  tube  of  the  third  set,  and  up 
the  annular  space  between  the  two.  It  is  claimed  that  by  this  system 
of  concentric  tubes,  complete  mixing  of  the  solution  of  the  reagents 
in  the  first  place,  and  complete  mixing  of  the  water  with  the  solutions 
in  the  second  place,  is  carried  out  very  thoroughly. 

After  the  mixing  tubes  there  are  treatment  vessels,  consisting  of 
tanks  of  various  forms,  according  to  convenience,  through  which  the 
liquid  is  obliged  to  pass  in  a  circuitous  course,  by  the  aid  of  baffles 
provided  for  the  purpose,  the  usual  precipitation  taking  place  in  this 
vessel.  From  the  treatment  vessel  the  softened  water  passes  suc- 
cessively through  two  sets  of  wood-wool  filters.  It  is  claimed  that 
the  primary  filter,  as  it  is  called,  through  which  the  water  first  passes, 


o;  -u 
O  o 


'So 


BOILER    ACCESSORIES 


'93 


SO6JTION  B 


MIXING  TUBC 


clarifies  it  thoroughly,  but  a  second  filter  is  added  to  make  sure.  The 
filters  require  cleaning,  the  primary  once  every  24  hours,  and  the 
secondaries  twice  a  week.  The 

fact  that  cleaning  is  required  is  I  |-O,L.V  WATER 

known  by  the  increased  pres- 
sure required  to  make  the  water 
pass  through  the  filter.  Fig. 
72  shows  diagrammatically  the  •# 

course  of  the  water  to  be  puri-     30^,0,^ 
fied,  and  Fig.  73  is  a  drawing 
of  the  apparatus,  showing  the 
different  vessels  through  which 
the  water  passes. 

When  lime  alone  is  used, 
one  compartment  of  the  dis- 
tributor is  arranged  with  a 
movable  wall,  enabling  the 
quantity  dealt  with  to  be  varied 
at  will.  The  water  from  this 
compartment  of  the  distributor 
is  carried  to  the  bottom  of  a 
tank,  of  moderate  depth,  charged 
with  a  mixture  of  slaked  lime 
and  water,  kept  in  motion  by 
a  blower  of  air.  The  lime  is 
slaked  in  a  separate  vessel,  and 
run  into  the  lime  tank  as  milk 

of  lime,  the  spent  lime  having  been  previously  removed.  The 
remainder  of  the  arrangement  is  similar  to  that  already  described. 


SLUDGE 


PvjRiriCD 


FIG.  72. — Diagram  showing  the  course  of 
the  Water  to  be  purified  in  the  Harris- 
Anderson  Apparatus. 


Removing  the  Oil  from  the  Water 

Kemoving  the  oil  from  the  water  is  a  very  much  more  difficult 
matter.  It  is  partly  accomplished  by  the  use  of  oil  separators,  of 
which  descriptions  are  given  below,  the  oil  separated  being  filtered 
and  used  again. 

Oil  Separators 

There  are  several  patterns  of  oil  separators,  all  of  which  are  con- 
structed on  very  much  the  same  lines.  They  usually  consist  of  a 
cylindrical  tank,  into  which  the  steam  is  allowed  to  enter  on  its  way 
to  the  condenser.  Within  the  tank  the  steam  is  usually  given  a 
more  or  less  circuitous  and  whirling  motion,  and  is  made  to  pass 

o 


i94     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

through  perforated  baffle  plates,  each  of  which  arrests  some  of  the  oil 
as  the  steam  passes  through,  and  it  is  claimed  that  all  oil  is  removed 
by  the  process. 

Fletcher's  oil  separator,  made  by  Messrs.  Eoyle,  consists  of  the 
usual  cylindrical  vessel,  with  an  inlet  for  the  steam  on  the  left,  and 


FIG.  73. — Drawing  showing  the  Harris-Anderson  Water-purifying  Apparatus. 

an  outlet  on  the  right.  The  space  is  divided  by  a  horizontal  tube- 
plate  just  below  the  line  of  the  main  steam  pipes,  and  again  by  a 
vertical  division  extending  from  the  top  to  within  a  short  distance  of 
the  tube  plate,  and  by  another  vertical  division  between  the  tube 
plate  and  the  top  of  the  apparatus.  There  are  tubes  passing  down 


BOILER   ACCESSORIES  195 

from  nearly  the  top  of  the  apparatus  through  the  tube  plate  into  the 
tank  below,  which  is  nearly  on  the  bottom  of  the  apparatus.  In 
the  right-hand  portion  there  are  also  tubes  held  by  the  tube  plate, 
leaving  a  free  space  above  and  below  them.  The  steam  entering 
is  accompanied,  it  is  found  in  the  inventor's  experience,  by  oil 
and  water,  these  keeping  to  the  lower  portion  of  the  entrance  pipe, 
and  being  carried  over  into  a  tube  on  the  left  of  the  apparatus, 
which  carries  them  to  the  bottom.  This,  it  is  claimed,  is  a  pre- 
liminary separation  of  the  oil  and  steam,  the  remainder  of  the 
apparatus  having  only  to  deal  with  the  oil  carried  over  in  the 
steam.  The  steam  passes  from  the  inlet  down  through  the  tubes 
in  the  left-hand  portion  into  the  water  in  the  tank,  where,  it  is 
claimed,  the  steam  is  further  cleansed  from  oil.  The  steam  then 
bubbles  up  through  the  water,  passes  up  on  the  outside  of  the  tubes 
through  which  it  descended,  over  the  top  of  the  partition  between  the 
two  compartments,  down  over  the  outside  of  the  tubes  in  the  right- 
hand  compartments,  up  through  the  tubes  in  that  compartment,  and 
thence  to  the  outlet.  It  is  claimed  that  the  steam  spaces  within 
the  apparatus  being  large  compared  with  the  steam  pipe,  the  steam 
is  not  throttled  in  any  way. 


Cochrane  Vacuum  Oil  Separator 

In  this  apparatus,  which  is  made  by  the  Erith  Engineering  Co., 
the  oil  is  caught  in  its  passage  through  a  vessel,  whose  area  is  large 
in  proportion  to  the  pipe  that  brings  the  steam  to  it,  by  a  baffle  plate 
occupying  the  centre  of  the  area,  and  fitted  with  ribs,  a  sufficient 
annular  space  being  provided  all  round  the  baffle  plate  to  allow  of 
the  passage  of  the  steam  without  throttling.  The  apparatus  is  made 
both  for  fixing  in  vertical  and  horizontal  pipes,  and  the  idea  in  its 
construction  is  that  the  heavier  oil  globules  will  be  caught  by  the 
central  baffle  plate,  while  the  lighter  steam  will  pass  by  the  annular 
passage  at  the  side. 


Reid  Oil  Separators 

In  the  Eeid  oil  separator,  sectional  drawings  of  which  are  shown, 
in  Fig.  74,  there  is  the  usual  iron  cylinder,  the  steam  entering 
through  the  central  pipe,  which  is  at  first  slightly  contracted,  and  then 
opens  out  into  a  bell  mouth.  The  depositing  chamber  is  at  the 
bottom  of  the  cylinder,  and  there  is  a  battery  of  corrugated  iron  plates, 
arranged  radially,  suspended  vertically  between  two  dished  plates, 
occupying  an  annular  space  above  the  depositing  chamber.  The 


196    STEAM  BOILERS,   ENGINES,   AND  TURBINES 


—  A 


IQ   74 —Vertical  and  Transverse   Section  of  Eeid's  Oil  Separator.    The  Steam 
enters  at  C,  passes  through  D  to  F,  and  then  up  between  the  corrugated  plates  K. 


BOILER   ACCESSORIES 


197 


steam  passes  up  between  the  corrugated  plates  and  through  an  outlet 
pipe.  The  action  of  the  apparatus  is  as  follows :  The  velocity  of  the 
steam  being  reduced  by  the  bell-mouthed  enlargement  of  the  entry 
pipe,  while  the  velocity  of  the  oil  or  grease  particles  is  not  so  much 
affected,  the  latter  are  thrown  forward  on  to  the  bottom  of  a  deposit- 
ing chamber.  This  cleanses  the  steam  to  a  large  extent  from  oil 
particles,  it  is  claimed,  and  the  remaining  particles  are  removed  by 
the  passage  of  the  steam  over  the  surfaces  of  the  corrugated  plates. 
The  inventor  claims  that  the  action  of  the  corrugated  plates  upon  the 
steam  is  similar  to  that  of  the  scrubber  in  a  gas-making  plant.  The 
oil  particles  are  caught  by  the  plates  and  run  down  into  the  de- 
positing chamber,  from  which  they  are  drained  off  in  the  usual  way. 


A  Steam  Exhaust  Head  and  Oil  Catcher 

It  is  sometimes  necessary  to  provide  some  means  of  preventing 
the  exhaust  steam,  where  engines  do  not  work  with  condensers,  and 
which  would  usually  be  delivered 
in  the  open  air,  from  being  thrown 
down  on  the  roofs  of  adjacent  build- 
ings, accompanied  by  the  oil  that 
has  been  carried  over  from  the 
engine  cylinders,  and  also  to  reduce 
the  noise  of  the  exhaust  steam  at 
each  stroke  of  the  engines,  that 
is  sometimes  objectionable.  There 
are  various  forms  of  exhaust  heads. 
One  is  shown  in  section  in  Fig. 
75,  made  by  Messrs.  Holden  and 
Brooke,  the  course  of  the  steam 
being  shown  by  the  arrows.  It 
will  be  seen  that  the  steam  enters 
by  the  inlet  pipe  at  the  bottom, 
passes  round  the  outside  of  the 
cup-shaped  vessel  in  the  centre, 
and  out  through  the  outlet  at 
the  top,  the  oil  and  condensed  FIG.  75.-Messrs.  Holden  &  Brooke's 
V  -  ,  Exhaust  Head  for  preventing  fine 

Steam    being    deposited    upon    the  particles  of  Oil  being  carried  out  to 

different    surfaces    over   which    it         the  neighbourhood, 
passes. 

Special  Apparatus  for  Removing  Oil 

There  are  two  kinds  of  apparatus  at  present  on  the  market  for 
removing  the  oil  from  exhaust  steam,  the  best  known  of  which  is  the 


198     STEAM   BOILERS,  ENGINES,   AND   TURBINES 


Harris  Anderson.  The  Harris  Anderson  apparatus  for  removing  oil 
is  very  similar  in  every  respect  to  that  for  softening  water,  except 
that  the  reagents  employed  are  carbonate  of  soda  and  sulphate  of 
alumina.  The  inventor  of  the  Harris  Anderson  apparatus  states  that 
he  has  found,  by  careful  microscopic  examination  of  condensed  water 
that  has  been  subjected  to  the  usual  separation  treatment  by  gravity, 
that  globules  of  oil  are  floating  about  in  the  water,  and  that  even  the 
filtration  by  the  very  closest  filtering  material  does  not  remove  them. 
After  oily  water  has  been  treated,  the  inventor  finds  that  the  globules 

of  oil  are  drawn  together. 
The  inventor  claims  that, 
by  the  addition  of  his  re- 
agents, and  by  the  work- 
ing of  his  process,  the  oil 
globules  are  caused  to 
coalesce,  and  can  then  be 
dealt  with  by  the  filters 
in  the  ordinary  way.  The 
working  of  the  apparatus 
is  practically  the  same  as 
that  of  the  water  softener. 


Davis  -Perrett's 

Electrical   Emul= 

sifier 

In  this  apparatus  com- 
pletely new  ground  has 
been  taken,  the  oil  being 
separated  from  the  water 
by  the  aid  of  electricity. 
In  the  apparatus,  a  diagram 
of  the  connections  of  which 
is  shown  in  Fig.  76,  the 
principal  portion  consists  of  a  number  of  wooden  tanks,  similar  to 
those  employed  for  electro-plating,  in  which  a  number  of  iron  or 
other  metallic  plates  are  suspended,  and  the  water  to  be  purified  is 
caused  to  pass  through  the  tanks  in  succession,  being  given  a  circuitous 
path,  so  that  it  is  obliged  to  pass  over  a  large  area  of  the  plates.  The 
electric  current  splits  up  the  water  and  the  oily  substances  mixed 
with  it,  by  the  well-known  property  of  electrolysis,  and  a  flocculent 
precipitate  is  formed  from  the  components,  combined  with  the  oxides 
of  the  metals  over  which  the  water  has  passed,  the  precipitate  being 
easily  removed  afterwards  by  a  filter. 


FIG.  76. — Diagram  of  Davis-Perrett's  Electrical 
Emulsifier.  The  Water  to  be  purified  is 
passed  through:  the  Electrolytic  Tanks  and 
then  through  the  Filter. 


BOILER   ACCESSORIES  199 

There  is  the  usual  preliminary  settling  tank  provided  with  the 
Davis-Perrett  apparatus,  in  which  a  certain  quantity  of  the  grosser  oil 
particles  separates  out  by  gravitation  and  is  recovered,  the  remainder 
of  the  water  then  flowing  to  the  electrolytic  tanks.  After  the  electro- 
lytic tank,  the  treated  water  flows  first  into  a  catch  tank,  where  a  certain 
further  precipitation  takes  place,  and  then  to  a  sand  filter.  Other  forms 
of  filter  are  also  provided  where  it  is  necessary,  and  the  water  then 
flows  from  the  bottom  of  the  filter,  through  a  sand  trap,  as  shown  in  the 
diagram,  to  the  hot  well.  The  makers  prefer  a  sand  filter,  as  it  is 
easily  cleaned  by  removing  the  upper  layer  of  sand.  The  plates  in 
the  electrolytic  tank  are  cleaned  automatically  by  reversing  the 
direction  of  the  current  through  them.  It  will  be  understood  that 
the  electrolytic  action  takes  place  principally  upon  one  set  of  the 
plates,  and  when  these  become  foul  the  reversal  of  the  current  looses 
the  scum  upon  them,  causing  it  to  float  to  the  surface,  where  it  can 
be  removed  by  skimming  in  the  usual  way.  The  following  are  the 
spaces  occupied  by  apparatus  for  treating  different  quantities  : — 

For  1000  gallons  per  hour  100  square  feet  floor  space  x  15  feet  to  20  feet  high 
„    2000        ,,  „        120 

„    4000        „  „         225 

,    8000  290 


Superheating  the  Steam 

Superheaters  perhaps  belong  properly  to  the  domain  of  steam 
engines,  but  they  are  usually  combined  directly  with  boilers,  and 
therefore  will  be  described  here,  and  their  use  discussed.  It  was 
explained  in  the  first  chapter  that  when  steam  is  formed  from  the 
water  in  a  boiler,  it  carries  over  with  it  into  the  steam  space  minute 
particles  of  water.  The  water  so  carried  forward  is  sometimes  in  the 
form  of  vapour,  sometimes  simply  in  the  form  of  finely  divided  water, 
but  in  all  cases  has  absorbed  a  very  much  smaller  quantity  of  heat 
than  the  steam  by  which  it  is  held  in  suspension.  The  water  particles 
and  the  vapour  particles  are  held  in  suspension  in  the  steam,  very 
much  as  dust  is  held  in  the  air,  and  as  the  mechanical  particles 
mentioned  are  held  in  water.  When  the  steam  containing  these 
particles  of  water  enters  a  steam  cylinder,  the  temperature  of  the 
walls  of  which  are  lower  than  that  of  the  steam  itself,  if  the  engine  is 
working  expansively,  as  will  be  explained,  the  temperature  of  the 
whole  of  the  steam  being  lowered,  its  ability  to  hold  the  water  in 
suspension  is  lowered,  and  the  particles  of  water  are  deposited  upon 
the  walls  of  the  cylinder,  taking  heat  from  them  at  a  later  portion  of 
the  stroke,  to  the  disadvantage  of  the  efficiency  of  the  engine. 

To  avoid  this,  the  steam  after  it  has  left  the  steam  space  in  the 


200    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

boiler,  and  therefore  when  it  is  out  of  contact  with  the  water 
from  which  it  was  formed,  is  exposed  to  further  heating,  either 
from  the  hot  gases  of  the  boiler  furnace  itself,  or  from  the  hot 
gases  of  a  separate  furnace  arranged  for  the  purpose.  In  either  case 
the  steam  is  made  to  pass  through  a  number  of  small  pipes,  between 
which  the  steam  is  split  up,  the  outside  of  the  pipes  being  exposed  to 
the  heat  of  the  hot  gases,  and  the  result  is  the  steam  is  dried.  That 
is  to  say,  the  particles  of  water  and  watery  vapour  that  are  held  in 
suspension,  are  converted  into  steam  at  the  same  temperature  as  that 
in  which  they  are  held,  and  the  steam  passes  on  to  the  engine  free 
from  the  presence  of  any  watery  vapour,  if  the  superheating,  as  it  is 
called,  has  been  properly  done. 

The  amount  of  superheat  arranged  in  different  cases  varies  from 
100°  F.  to  300°  F.,  150°  F.  being  a  common  figure,  and  it  is  understood 
that  the  whole  of  the  steam  passing  through  the  superheater  has  its 
temperature  raised  by  that  number  of  degrees,  the  water  and  watery 
vapour  carried  in  suspension  being  raised  to  steam  at  the  final 
temperature.  The  quantity  of  heat  required  to  perform  the  operation 
of  superheating  evidently  depends  upon  the  quantity  of  water  and 
watery  vapour  present.  This  has  been  determined  by  the  principal 
boiler  makers,  and  their  superheaters  are  constructed  to  furnish  the 
largest  quantity  of  heat  that  may  be  required,  under  the  worst  con- 
ditions of  moisture  present.  It  should  be  mentioned  incidentally  that 
watery  vapour  is  more  readily  carried  over  with  the  steam  when 
boilers  are  forced,  and  that  it  is  claimed  by  advocates  of  Lancashire 
and  similar  boilers  that  water- tube  boilers,  though  they  will  raise 
steam  very  readily,  are  subject  to  this  action  of  priming  when  the 
boilers  are  forced.  The  quantity  of  watery  vapour  present  in  the 
steam  is  estimated  by  means  of  an  apparatus  designed  for  the  pur- 
pose, called  a  calorimeter,  the  operation  of  which  consists  either  in 
separating  the  water  carried  by  the  steam  from  it,  in  a  sensitive 
apparatus  arranged  for  the  purpose;  or  in  estimating  the  moisture 
present  in  a  measured  quantity  of  steam  by  forcing  it  through  a 
small  passage,  leading  from  a  higher  to  a  lower  pressure,  and 
measuring  the  degrees  of  superheat  given  to  the  steam.  When 
moisture  is  present  the  superheating  will  be  less  by  the  heat  absorbed 
by  the  moisture. 


Forms  of  Superheating  Apparatus 

The  Babcock  Wilcox. — The  Babcock  Wilcox  superheater, 
which  is  shown  in  Plate  SA,  in  connection  with  the  boiler,  consists 
of  a  number  of  (J'tubes  fixed  horizontally,  immediately  below  the 
steam  drum.  As  will  be  seen,  there  is  a  baffle  below  the  lower 


BOILER   ACCESSORIES 


201 


portion  of  the  superheater,  and  it  is  exposed  to  the  full  force  of  the 
hot  gases  rising  directly  from  the  furnace. 


FIG.  77. — Tinker's  Superheater,  as  fitted  to  a  Lancashire  Boiler.  The  Steam  to  be 
heated  passes  through  the  Coils  of  Pipes  shown,  the  Pipes  being  fixed  in  the 
Path  of  the  Hot  Gases  from  the  Boiler  Flues  to  the  Chimney. 

The  Stirling  Superheater.— The  Stirling  superheater  is  shown 
in  Fig.  12,  and,  as  will  be  seen,  consists  of  a  number  of  tubes,  fixed 


202     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

between  two  smaller  drums,  the  tubes  lying  in  the  space  between  the 
foremost  and  second  bank  of  the  boiler  tubes,  so  that  they  are  subject 
to  the  hot  gases  in  the  earlier  portion  of  their  travel. 


FIG.  78. — Schmidt's  Superheater  arranged  for  heating  by  Boiler  Flue  Gases.     It  is 
shown  at  the  back  of  a  Lancashire  Boiler. 

The   Nesdrum  Superheater. — The  Nesdrum  superheater  con- 
sists of  a  number  of  tubes  of  a  zigzag  form,  fixed  between  the  steam 


FIG.  79. — Longitudinal  and  Transverse  Section  of  Schmidt's  Superheater,  arranged 
for  direct  firing.     The  Furnace  for  the  Superheater  is  shown  below. 


drum  and   the  exit  steam  pipe,   the  tubes  lying  in  the  rear  space 
between  the  vertical  tubes  and  the  next  bank  in  front  of  them. 


BOILER   ACCESSORIES  203 

The  Sinclair  Superheater — The  Sinclair  superheater  consists 
of  U  -tubes,  fixed  vertically  in  a  space  provided  for  them  at  the 
back  of  the  boiler,  on  the  way  to  the  chimney,  by  means  of  a  baffle 
in  front  of  the  rear  wall.  They  receive  heat  from  the  hot  gases  after 
they  have  done  their  work  upon  the  whole  of  the  boiler  tubes. 

The  Galloway  Superheater. — The  Galloway  superheater  is 
arranged  to  be  fixed  in  the  downtake  at  the  back  of  Galloway  and 
other  Lancashire  boilers,  so  that  it  is  subjected  to  the  hot  gases 
immediately  after  they  leave  the  main  boiler  flues.  It  consists  of 
a  number  of  U -tubes,  connected  to  a  top  plate,  to  which  the  steam 
is  led  from  the  boiler,  and  from  which  it  is  taken  after  having 
passed  through  the  tubes. 

The  Tinker  Superheater. — The  Tinker  superheater,  which  is 
shown  in  Fig.  77,  consists  of  two  banks  of  tubes,  approximately  of  U 
form,  fixed  vertically  in  the  downtake  of  Lancashire  boilers,  the  steam 
passing  through  the  two  sets  in  succession,  and  the  superheater  pipes 
being  subjected  to  the  hot  gases  in  a  similar  manner  to  the  Galloway. 
The  Schmidt  superheater,  made  by  Easton  and  Co.,  is  arranged  for 
heating  from  the  flue  gases,  as  shown  in  Fig.  78,  or  for  separate  firing, 
as  shown  in  Fig.  79.  It  consists  of  grids  of  pipes  fixed  horizontally, 
the  flue  gases  passing  up  between  the  pipes. 


Steam  Separators 

The  steam  separator  is  another  auxiliary  apparatus  that  has  been 
introduced  for  the  purpose  of  drying  the  steam,  when  superheaters  are 
not  employed,  and  also  for  removing  any  watery  vapour  that  may  be 
present  in  other  positions,  and  preventing  it  going  into  the  steam 
engine.  They  are  all  arranged  on  something  the  same  lines,  the 
principle  of  which  is,  the  bringing  into  play  the  force  of  gravity, 
acting  upon  the  greater  weight  of  the  watery  particles,  and  causing 
them  to  be  deposited.  Steam  separators  are  very  similar  in  many 
respects  to  some  of  the  oil  separators  that  have  been  described. 
They  consist  usually  of  a  vessel,  into  which  the  steam  is  carried,  and 
in  which  it  is  given  a  more  or  less  circuitous,  and  sometimes  a 
whirling  path,  and  in  which  there  are  a  certain  number  of  baffle 
plates,  these  latter  arresting  the  watery  particles  while  the  steam 
passes  on,  the  water  draining  to  the  bottom  of  the  vessel  and  being 
removed  by  a  cock  provided  for  it. 

The  Marriot  Steam  Separator. — In  this  apparatus,  which  is 
intended  for  separating  oil,  water,  dirt,  and  grease  from  the  steam, 
there  is  the  usual  vertical  cylinder,  surmounted  by  a  cylindrical 
casting,  with  inlet  and  exit  pipes  for  the  steam.  In  the  central 
portion  of  the  upper  vessel,  and  the  chamber  below,  a  number  of 


204    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

iron  rods  of  various  sections  are  fixed  vertically,  and  the  idea  of  the 
inventor  is,  that  the  steam  passing  through  the  apparatus  will  be 
diverted  by  the  outer  edges  of  the  rods,  and  that  a  cushion  of  steam 
will  be  left  in  the  concave  spaces  into  which  water,  oil,  and  other 
impurities  will  be  thrown,  the  steam  escaping  past  them  to  the  outlet, 
and  the  water  and  oil,  etc.,  trickling  down  to  the  bottom  of  the  vessel, 
where  they  are  run  off  in  the  usual  way.  Fig.  80  shows  the  Sims 


FIG.  80. — The  Sims  Steam  Separator,  for  fixing  in  a  Horizontal  Pipe.  F  is  a 
Deflector  arranged  for  the  Steam  to  be  thrown  against,  and  E  is  a  Well  into 
which  the  separated  Water  drains. 

steam  separator,  an  American  apparatus.  The  steam  is  given  a 
whirling  motion  inside  the  apparatus,  and  is  thrown  up  against  the 
deflectors  shown,  the  water  being  left  there,  and  draining  down  into 
the  well  below. 

Evaporators 

The  evaporator  is  another  auxiliary  apparatus,  employed  prin- 
cipally on  board  ship,  where  it  is  of  such  great  importance  that  the 


BOILER   ACCESSORIES  205 

feed  water  shall  be  absolutely  pure,  to  make  up  the  waste.  In 
steam  engine  practice,  where  condensers  are  employed,  the  water 
from  which  the  steam  was  generated  in  the  boiler  again  becomes  water 
in  the  condenser,  as  explained  later,  and  is  used  in  many  cases, 
nearly  always  on  board  ship,  for  feeding  the  boiler.  But  there  is 
always  a  certain  small  loss  between  the  steam  which  leaves  the 
boiler  and  the  water  which  re-enters  it  after  having  done  its  work  in 
the  engine,  and  been  condensed.  There  is  nearly  always  a  certain 
amount-  of  leakage  of  steam  at  different  parts  of  the  engine  system. 
There  is  also  a  certain  amount  of  loss  by  condensation,  the  water  so 
formed  being  drained  off  by  steam  traps  provided  for  the  purpose, 
and  being  lost  so  far  as  the  steam  system  is  concerned.  Hence  a 
certain  quantity  of  fresh  water  is  required  to  make  up  the  loss,  and 
this  is  provided  in  modern  steamships  by  the  aid  of  an  evaporator. 
Evaporators  are  of  various  forms,  but  all  conform  to  certain  conditions. 
In  all  of  them  there  are  two  parts  to  the  apparatus,  one  in  which  sea 
water,  or  the  water  that  is  to  be  employed  for  making  up,  is  caused 
to  evaporate  at  very  low  pressure,  and  the  other  in  which  the  vapour 
so  formed  is  recondensed  into  water  and  carried  off  to  the  hot  well  or 
to  the  boiler. 

High-pressure  steam  is  employed  as  the  heating  agent  in  that 
portion  in  which  the  water  is  evaporated.  In  one  such  apparatus, 
made  by  Messrs.  Koyle,  steam  is  passed  through  tubes,  while  the 
water  surrounds  them,  and  is  formed  into  vapour.  The  upper  portion 
of  the  apparatus  is  a  condenser,  to  which  the  vapour  formed  in  the 
evaporator  rises,  and  where  it  passes  through  tubes,  around  which 
cold  water  is  circulated,  the  vapour  being  then  formed  into  distilled 
water. 

The  apparatus  is  also  employed  for  distilling  water  for  drinking, 
etc.,  on  board  ship,  if  the  supply  gives  out.  Plate  10A  shows  an 
evaporator  made  by  the  Central  Engineering  Co.,  Hartlepool.  Fig.  81 
is  a  sectional  diagram  of  Weir's  vertical  type  of  evaporation. 

Apparatus  for  Testing  the  Flue  Oases  in  the 

Chimney 

In  recent  years  sources  of  economy  in  steam  and  coal  have  been 
considerably  multiplied,  but  it  has  been  felt  that  some  means  is 
necessary  for  checking  the  results.  Thus,  good  boilers,  mechanical 
stokers,  good  draught,  and  everything  that  is  necessary  to  economy 
may  be  provided,  and  yet  from  certain  causes  the  results  may  not  be 
as  economical  as  would  be  hoped,  and  every  means  of  testing  the 
results,  and  every  means  of  testing  from  point  to  point  of  the  steam 
system,  is  of  value.  In  modern  plant  the  coal  is  all  weighed  into 


206    STEAM   BOILERS,   ENGINES,  AND  TURBINES 


PP~','--O — ~O O" O O""T  1Q">\  xi 

in  •' v      j-\  >n> 


o--— -GX----O— --o — c>-:' 


FIG.  81. — Sectional  Drawing  of  Weir's  Vertical  Evaporator,  with  the  lower  portion 
open.  The  Water  is  evaporated  in  the  lower  portion  and  recondensed  in  the 
upper  portion. 


BOILER   ACCESSORIES 


207 


PERCENTAGE    OF  FUEL     LOST 
1O    2O    30  4O    5O    OO    W    8O   9O  tOO 


the  hopper  of  the  boiler  furnace,  the  water  is  usually  measured,  so 
that  a  check  is  kept  upon  the  consumption,  and,  in  addition,  the 
apparatus  to  be  described  has  been  designed  for  testing  the  fuel  gases 
in  the  chimney.  It  was  explained  in  the  first  chapter  that  a  certain 
quantity  of  air  must  be  supplied  for  each  pound  of  fuel  that  is  to  be 
burned,  because  that  quantity  of  air — 12  Ibs.  at  average  temperatures 
— will  furnish  the  necessary  quantity  of  oxygen  to  completely 
oxidize  the  pound  of  carbon  to  carbonic  acid.  It  follows  from  this 
that  if  exactly  the  right  quantity  of  air  is  furnished,  and  if  the  whole 
of  the  oxygen  combines  with  the  whole  of  the  carbon,  assuming  that 
only  carbon  is  present,  the  resultant  gases  must  consist  of  nitrogen 
and  carbonic  acid,  in  the  same  proportion  as  the  air  consisted  of 
nitrogen  and  oxygen,  or  the 
carbonic  acid  present  must  be 
21  per  cent,  of  the  resultant 
gases.  It  was  also  pointed 
out  that  it  is  not  possible  to 
work  with  the  exact  quantity 
of  air  that  will  furnish  the 
correct  quantity  of  oxygen. 
More  frequently  double  the 
quantity  of  air  is  provided, 
and,  in  addition,  coal  is  not 
all  carbon.  It  often  contains 
some  uncombined  hydrogen ; 
and  it  also  contains  other 
substances,  known  generically 
as  ash.  It  is  found,  however, 
that  a  test  of  the  fuel  gases, 
to  show  what  percentage  of 
carbonic  acid  is  present,  is 
also  an  approximate  test  of 

the  way  in  which  combustion  is  going  on  in  the  boiler  furnace. 
With  all  the  carbon  combined  with  oxygen,  and  with  no  surplus 
air,  and  with  no  other  substances  present,  the  fuel  gases  should  show 
21  per  cent,  of  carbonic  acid.  At  the  other  end  of  the  scale,  if  none 
of  the  carbon  combines  with  oxygen  no  carbonic  acid  will  be  formed. 
Obviously,  between  these  two  there  are  various  degrees,  and  in  the 
curve  shown  in  Fig.  82  the  various  possible  percentages  of  C02 
present  in  the  fuel  gases  have  been  plotted,  and  with  them  the 
percentages  of  loss  of  fuel.  The  ordinates  represent  percentages  of 
C02,  and  the  abcissae  represent  percentages  of  fuel  lost.  At  the 
origin  no  fuel  is  lost,  and  at  the  end  of  the  curve  of  course  the 
whole  of  the  fuel  is  lost.  It  will  be  noticed  that  the  curve,  which 
is  parabolic,  rises  very  steeply  for  a  certain  portion,  and  then  turns 


1 

I  I  I 

1  _J 

fU£L  LOST 

„, 

t^ 

^ 

** 

4 

^ 

-" 

J 

/ 

•£ 

/ 

y  __ 

/ 

ft 

/ 

.0 

/ 

10 

/ 

11 

/ 

12 

13 

FUEL  USED 

14 

I 

15 

I 

16 

17 

I 

ffl 

I 

W- 

PIG.  82. — Showing  the  percentage  of  Fuel 
lost,  with  different  percentages  of  C02 
in  the  Flue  Gases. 


208    STEAM  BOILERS,   ENGINES,   AND   TURBINES 

rather  rapidly,  the  meaning  of  this  being  that  the  percentages  of  loss 
of  fuel  increase  very  slowly  with  decreased  percentages  of  carbonic 
acid,  down  to  12  per  cent,  of  C02,  after  which  the  losses  increase 
rapidly.  It  is  stated  that  a  loss  of  12  per  cent,  of  fuel,  correspond- 
ing to  a  percentage  of  15  per  cent,  of  C02,  is  the  best  result  obtain- 
able in  practice,  while  results  such  as  from  7  to  8  per  cent,  of  C02, 
meaning  losses  of  from  22  to  25  per  cent,  of  fuel,  are  very  common. 


The  Sarco  Automatic  CO2  Recorder 

The  Sarco  apparatus  is  intended  to  note  on  a  chart  provided  for 
the  purpose,  the  percentage  of  C02  in  the  fuel  gases  from  hour  to 
hour,  so  that  the  actual  working  of  the  boilers,  and  the  attention 
the  furnaces  have  received,  can  be  checked  from  time  to  time. 

There  are  two  forms  of  the  apparatus,  one  worked  by  water  and 
the  other  by  the  fuel  gases  themselves.  Both  are  arranged  to  furnish 
a  definite  quantity  of  the  fuel  gases  at  certain  definite  intervals,  as 
may  be  arranged  by  the  engineer.  In  both  there  is  a  pipe  connect- 
ing the  end  of  the  flue,  or  the  beginning  of  the  chimney,  at  any 
convenient  point,  with  the  apparatus,  the  connection  being  made  by 
a  piece  of  flexible  gas  tube,  and  there  is  practically  a  pump  worked 
either  by  the  fuel  gases  or  by  water,  drawing  a  certain  quantity  of  the 
gases  passing  at  the  moment  into  the  apparatus,  the  connection  to 
the  flue  being  closed  as  soon  as  the  required  quantity  has  been  drawn 
off,  and  automatically  reopened  as  soon  as  measurement  has  taken 
place.  The  measurement,  as  explained,  is  of  the  percentage  of  C02 
in  the  flue  gases,  and  it  is  accomplished  by  the  absorption  of  the 
C02  contained  in  the  sample  of  the  gases  drawn  off  at  each  stroke  of 
the  pump,  the  amount  absorbed  being  measured  on  a  scale,  and  at 
the  same  time  a  pencil  marking  the  quantity  on  a  chart,  in  the  form 
of  a  vertical  line,  as  shown.  The  pump  in  which  flue  gases  are 
employed  is  very  similar  to  one  of  the  forms  of  pump  used  for 
compressing  illuminating  gas  for  use  in  high-pressure  burners.  It 
consists  of  a  cylinder  with  a  second  cylinder  fixed  concentrically 
inside  it,  the  cylinder  and  the  annular  space  being  filled  with  water 
to  a  certain  height,  and  a  bell,  similar  to  that  employed  in  gaso- 
meters but  very  much  smaller,  dipping  into  the  water,  forming  the 
usual  water  seal.  From  the  top  of  the  bell  a  rope  passes  over  a 
pulley  above,  and  is  secured  to  a  counter-weight,  the  counter-weight 
also  being  attached  on  its  under  side  to  a  bottle  filled  with  glycerine 
and  water,  and  forming  a  part  of  the  testing  apparatus.  A  tube  is 
connected  to  the  inside  of  the  bell,  and  by  means  of  a  pipe,  forming 
part  of  it,  to  the  flue  gases,  the  connection  being  made  by  a  flexible 
tube.  The  pressure  in  the  flue  being  less,  it  will  be  remembered, 


BOILER  ACCESSORIES 


209 


than  the  atmosphere  outside,  when  connection  is  made  between  the 
inside  of  the  bell  and  the  flue,  the  air  in  the  bell  is  drawn  out,  the 
bell  then  sinking  in 
the  containing  vessel, 
and  drawing  down 
the  counter  -  balance 
weight  and  revolving 
the  pulley  above.  The 
pulley  carries  two 
studs,  which  are  alter- 
nately brought  into 
contact  with  a  lever 
just  below  the  pulley, 
which  controls  a  valve, 
closing  and  opening 
the  connection  between 
the  flue  and  the  bell. 
When  the  bell  has 
fallen  to  a  certain 
depth,  connection  with 
the  flue  is  shut  off,  and 
air  is  admitted  to  the 
bell,  causing  it  to  rise, 
the  pulley  revolving 
in  the  opposite  direc- 
tion, bringing  the  other 
stud  into  contact  with 
the  lever,  throwing 
open  the  valve  leading 
to  the  flue  gases,  shut- 
ting off  the  atmosphere, 
and  opening  a  passage 
to  the  flue.  The  bell 
now  falls  again,  and 
so  on.  On  the  right 
of  the  apparatus,  as 
shown  in  Fig.  83,  are 
two  smaller  pumps, 
worked  by  one  rope 
or  wire,  passing  over  a 
smaller  pulley  carried 
on  the  same  axle  as 

the  pulley  moved  by  the  bell,  and  also  over  the  two  guide  pulleys, 
as  shown.  The  two  smaller  pumps  are  arranged  on  the  same  lines 
as  the  larger  one,  but  they  have  oil  seals  instead  of  water  seals,  and 

p 


FIG.  83. — Sectional  Elevation  of  "Sarco"  Flue  Gas 
Testing  Apparatus,  made  by  Messrs.  Sanders, 
Kehder  &  Co. 


210    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

their  office  is  to  pump  gas  from  the  flue  into  the  measuring  apparatus 
shown  in  the  diagram  in  Fig.  83.  The  measuring  apparatus  con- 
sists of  a  system  of  tubes,  in  connection  with  the  lower  part  of  a 
bottle  containing  glycerine  and  water  that  is  carried  by  the  counter- 
balance weight.  As  the  pump  rises  and  falls,  and  the  small  pumps 
rise  and  fall,  the  gas  is  pumped  alternately  into  these  tubes,  from 
which  it  passes  over  into  a  conical  vessel  filled  with  caustic  potash. 


FIG.  84. — Diagram  of  the  Simmance  and  Abady  Flue  Gas-testing  Apparatus. 


Caustic  potash  has  the  property  of  absorbing  COz,  and  evidently  the 
quantity  of  gas  present  will  be  less  by  the  amount  of  C02  absorbed. 
The  tubes  mentioned,  and  another,  are  arranged  so  that  a  definite 
quantity  of  the  gases — 100  cubic  centimetres — are  taken  for  measure- 
ment at  each  stroke  of  the  pump,  and  the  quantity  of  C02  present  is 
shown  by  the  position  of  a  small  tube,  which  works  a  lever,  at  one 
end  of  which  is  a  counter-balance,  and  at  the  other  end  a  rod  carry- 
ing a  pencil,  which  moves  up  and  down  over  the  chart.  The  chart 


BOILER   ACCESSORIES 


211 


is  revolved  in  the  usual  way  by  clock-work,  and 
merely  straight  lines,  whose  edges  form  a  curve. 

In  the  Sarco  apparatus, 
known  as  type  B,  which  is 
the  form  shown  in  Fig.  83, 
the  arrangement  is  very  simi- 
lar, but  rather  more  compact, 
and  the  pump  is  worked  by 
water.  Clean  water  is  re- 
quired, though,  providing  it 
is  clean,  any  kind  of  -  water 
will  do;  and  from  2  to  5 
gallons  per  hour  are  required 
to  drive  the  machine,  accord- 
ing to  the  speed  at  which  it 
is  operated.  The  water  must 
have  a  head  of  about  2  feet 
in  order  to  operate  the  appa- 
ratus, and  may  be  used  over 
and  over  again. 


the  indications  are 


The  Simmance  and 
Abady  CO2  Recorder 

In  this  apparatus,  which 
is  made  by  Messrs.  Alexander 
Wright  &  Co.,  a  diagram  of 
which  is  shown  in  Fig.  84, 
the  arrangement  is  very  simi- 
lar in  principle,  but  the  motor 
which  pumps  the  flue  gases 
into  the  apparatus  is  always 
worked  by  water,  and  the 
general  arrangement  is  rather 
simpler  than  that  of  the 
Sarco.  The  quantity  of  flue 
gas  taken  from  the  flues  is 
measured,  as  in  the  Sarco 
apparatus,  by  filling  a  vessel 
of  a  certain  capacity  at  each 
stroke  of  the  pump,  the 
working  of  the  apparatus  being  automatic.  The 
termed  by  the  inventors,  is  different  from  that 
is  shown  at  R  in  the  figure,  and  consists  of  an 


analyzer,  as  it  is 
in  the  Sarco.  It 
inverted  cylinder, 


212    STEAM  BOILERS,  ENGINES,  AND  TURBINES 

passing  into  a  tank  filled  with  caustic  potash,  this  forming  the  usual 
seal,  and  the  bell  contains  a  number  of  concentric  tubes  in  communi- 
cation with  each  other,  their  surfaces  being  wetted  with  the  caustic 
potash  solution.  The  flue  gases  to  be  measured  are  made  to  pass 
into  the  bell,  and  over  the  whole  of  the  surfaces  of  the  concentric 
tubes,  and  the  quantity  of  CGj  absorbed  is  measured  by  the  amount 
the  bell  falls,  this  being  marked  on  the  scale  S,  shown  on  the  right, 
and  also  by  a  line  on  the  chart,  as  with  the  Sarco.  Fig.  85  shows 
two  charts  taken  with  the  Simmance  and  Abady  apparatus. 

The  Orsat  Apparatus  for  Flue  Gas  Analysis 

This  apparatus  is  designed  for  a  more  accurate  analysis  of  the 
flue  gases,  but  it  does  not  give  a  continuous  record,  as  the  others  that 
have  been  described  do.  It  has  three  absorbing  apparatus,  designed 
to  absorb  carbonic  acid,  oxygen,  and  carbonic  oxide,  the  absorption  of 
these  forming  a  complete  analysis  of  the  flue  gases.  It  will  be 
evident  that  while  the  apparatus  that  have  been  described  for  giving 
a  continuous  record  of  the  carbonic  acid  present  in  the  flue  gases, 
forms  a  very  valuable  check  upon  the  stoking  and  the  working  of 
the  boilers  generally,  it  is  not  so  complete  as  the  analysis  which 
gives  the  full  percentage  of  the  other  gases  present.  In  the  vessel  ; 
that  is  to  absorb  carbonic  acid,  a  solution  of  caustic  potash  is  held, 
made  by  dissolving  one  part  by  weight  of  caustic  potash  in  2% 
parts  of  water;  in  that  for  oxygen,  pyrogallol,  made  by  dissolving 
one  part  by  weight  of  pyrogallic  acid  in  two  parts  of  hot  water,  and 
three  parts  of  the  caustic  potash  solution  made  for  the  absorption 
of  CQ&  In  the  vessel  for  absorbing  carbonic  oxide,  a  solution  of 
cuprous  chloride  is  held,  made  by  dissolving  one  part  by  weight  of 
cuprous  chloride  in  seven  parts  of  hydrochloric  acid,  adding  two 
parts  of  copper  clippings,  allowing  to  stand  for  twenty-four  hours, 
and  then  adding  three  parts  of  water. 

As  in  the  other  apparatus  described,  exactly  100  cubic  centi- 
meters of  the  flue  gases  are  drawn  for  examination,  and  are  passed 
into  a  graduated  measuring  burette.  The  measuring  burette  is 
surrounded  by  a  vessel  of  water,  so  that  the  temperature  of  the  gas 
in  the  burette  may  be  maintained  constant.  The  lower  part  of  the 
burette  is  connected  to  a  bottle  by  a  flexible  tube,  and  the  gases  are 
drawn  into  the  burette,  and  thence  forced  into  the  absorption  vessels 
in  succession,  by  raising  and  lowering  the  bottle,  and  opening  the 
cocks  leading  to  the  different  vessels  in  succession,  For  rapid  work, 
an  aspirator  must  be  employed  to  draw  the  gas  into  the  apparatus. 


CHAPTER   IV 

THE  STEAM  ENGINE 

The  Reciprocating  Steam  Engine 

THE  term  "  reciprocating  "  is  employed  to  distinguish  what  was  pre- 
viously known  simply  as  the  steam  engine  from  the  turbine,  which 
is  also  a  steam  engine,  but  in  which  the  moving  parts  do  not  recip- 
rocate. In  the  reciprocating  engine,  as  usually  understood,  there  are 
one  or  more  hollow  cylinders,  closed  at  each  end,  in  each  of  which  a 
solid  short  cylinder,  called  the  piston,  reciprocates,  or  moves  to  and 
fro,  the  reciprocating  motion  being  communicated  from  the  piston  to 
a  rod,  fixed  in  its  centre,  and  projecting  through  a  hole  provided  for 
it  in  one  end  of  the  cylinder,  and  from  it  usually  to  a  crank  shaft. 
In  nearly  all  forms  of  reciprocating  engines,  the  steam  is  admitted 
alternately  on  each  side  of  the  piston.  When  admitted  on  one  side 
of  the  piston,  the  piston  is  forced  forward  to  the  other  end  of  the 
cylinder,  carrying  the  piston-rod  with  it,  and  on  its  arrival  there, 
steam  is  admitted  to  the  other  side,  and  it  is  then  forced  back  to  the 
end  of  the  cylinder  from  which  it  started,  steam  being  then  admitted 
to  the  side  against  which  it  first  pressed,  and  so  on ;  the  to  and  fro 
movement  continuing  as  long  as  the  steam  is  available,  the  admission 
valves  are  working  properly,  and  the  work  in  front  of  the  engine  is 
not  greater  than  the  steam  can  accomplish. 

There  are  a  few  forms  of  single-acting,  reciprocating  engines,  a 
notable  example  being  the  Willans,  which  is  described  on  p.  232. 
In  the  old  Cornish  pumping  engines  also,  which  held  their  own  for 
economy  in  steam  against  other  forms  of  engines  employed  for  pumping 
up  till  very  recently,  the  steam  was  admitted  only  on  the  under  side 
of  the  piston,  the  cylinder  being  fixed  vertically,  and  the  piston  being 
moved  upwards  by  the  force  of  the  steam,  and  being  allowed  to 
descend  by  the  force  of  gravity,  aided  by  the  fact  that  the  steam 
under  the  piston  was  condensed,  and  therefore  the  pressure  below  the 
piston  was  reduced  considerably  below  that  of  the  atmosphere.  As 
the  cylinders  were  made  very  large,  6  and  8  feet  in  diameter,  the 

213 


2i4    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

effect  of  the  difference  between  the  pressure  of  the  atmosphere  and 
that  of  the  partial  vacuum  under  the  piston,  was  considerable. 

In  the  early  forms  of  steam  engines,  the  steam  was  admitted  to 
the  cylinder  without  any  attempt  at  what  is  called  working  expan- 
sively. Practically  the  action  of  the  steam  in  those  days,  and  in 
some  old  engines  even  up  to  the  present,  is  the  same  as  that  of 
water  in  a  reciprocating  water  engine. 

The  steam  was  continuously  generated  in  the  boilers,  and  as  long 
as  the  "  stop  valve "  leading  to  the  steam  chest  of  the  engine  was 
open,  the  steam  merely  pushed  the  piston  from  one  end  of  the 
cylinder  to  the  other,  and  back  again.  This  arrangement  holds  even 
yet  in  some  forms  of  steam  pumps,  but  for  the  majority  of  steam 
engines,  expansive  working  has  been  introduced,  and  gradually 
increased.  It  will  easily  be  understood  that  if  the  steam  cylinder 
is  open  to  the.  boiler,  during  the  whole  of  its  stroke,  it  will  use  a 
cylinder  full  of  steam,  less  the  space  occupied  by  the  piston,  at  each 
stroke ;  while  the  steam  which  is  ejected  from  the  cylinder  on  the 
return  stroke,  will  contain  a  large  portion  of  the  energy  with 
which  it  entered  the  cylinder,  and  unless  it  is  condensed,  will  offer 
a  considerable  resistance  to  the  return  of  the  piston,  so  that  there  is 
a  waste  of  steam,  and  of  coal,  from  both  causes.  If  in  place  of 
allowing  the  valve  controlling  the  entrance  of  the  steam  on  each 
side  of  the  piston  to  be  open  during  the  whole  of  the  stroke,  it  is 
closed  when  the  piston  has  made  half  the  stroke,  it  will  be  evident 
that  if  the  steam  is  able  to  complete  the  stroke  of  the  piston,  the 
work  will  have  been  accomplished  by  the  use  of  only  half  the  quan- 
tity of  steam,  and  the  pressure  resisting  the  return  of  the  piston, 
will  be  considerably  decreased.  In  expansive  working,  this  is  what 
is  done.  The  entrance  of  the  steam  to  the  cylinder  is  cut  off  at 
varying  points  of  the  stroke,  at  f ,  J,  f ,  J,  down  to  ^0-.  The  steam 
is  expanded  as  many  times  in  the  passage  of  the  piston  to  the  end 
of  the  stroke,  as  the  cut-off  is  proportionate  to  the  whole  of  the 
stroke.  Thus,  with  cut-off  at  half  stroke,  the  steam  is  expanded 
twice,  or  to  twice  its  volume.  With  steam  cut  off  at  |,  it  is  expanded 
four  times,  with  cut-off  at  ^  it  is  expanded  ten  times,  and  so  .on. 
As  explained,  the  remaining  work  of  forcing  the  piston  to  the  end  of 
its  stroke  is  performed  by  the  expansion  of  the  steam.  It  will  be 
remembered  that  with  gases — and  for  this  purpose  steam  may  be  con- 
sidered as  a  gas — the  equation  pv  =  a  constant,  rules.  That  is  to  say, 
if  the  volume  is  increased,  the  pressure  is  decreased  in  the  same  pro- 
portion. Thus,  when  the  steam  is  cut  off  at  half  stroke,  and  the 
space  occupied  by  the  steam  at  the  end  of  the  stroke  is  double  that 
occupied  when  cut  off,  the  pressure  at  the  end  of  the  stroke  will  be 
half  that  at  which  it  was  cut  off.  When  the  steam  is  cut  off  at  j 
stroke,  the  pressure  will  be  j  that  figure  at  the  end  of  the  stroke, 


THE   STEAM   ENGINE  215 

and  so  on.  But  the  working  pressure,  that  operating  to  force  the 
piston  through  the  remainder  of  the  stroke,  after  steam  is  cut  off, 
will,  it  is  evident,  be  a  gradually  decreasing  one,  as  the  pressure 
gradually  decreases  as  the  volume  of  the  steam  increases,  and  the 
pressure  operating  through  the  remainder  of  the  stroke  will  be  a 
mean  of  all  the  pressures  the  steam  passes  through  during  that 
portion. 

The  Mean  Effective  Pressure 

By  the  mean  effective  pressure  is  meant,  the  mean  of  all  the 
pressures  through  which  the  steam  passes  from  the  moment  of  its 
entry  into  the  cylinder,  to  the  end  of  the  stroke.  In  the  case  of 
very  late  cut-offs,  the  mean  effective  pressure  will  be  very  nearly 
that  of  the  pressure  at  which  the  steam  entered,  because  that  pressure 
will  be  effective  for  a  large  portion  of  the  stroke,  and  the  final 
average  will  not  be  greatly  reduced.  On  the  other  hand,  with  very 
early  cut-offs,  the  initial  pressure  of  the  steam  being  only  present 
during  a  very  small  portion  of  the  stroke,  will  have  only  a  small 
effect  upon  the  final  average. 

In  Table  XX.  the  mean  effective  pressures  are  given  for  different 
steam  pressures,  and  for  different  cut-offs,  from  -^  of  a  stroke  upwards, 
and  from  0  absolute  pressure  up  to  200  Ibs.  per  square  inch. 

It  was  pointed  out  in  Chapter  I.  that  considerable  advantage  was 
obtained  by  working  with  steam  at  higher  pressures  than  ruled  in 
the  early  days  of  steam  working,  because  the  quantity  of  heat  required 
to  produce  a  pound  of  steam  decreased  as  the  pressure  increased, 
and  therefore  if  the  whole  of  the  pressure  could  'be  effectively  em- 
ployed in  the  engine,  economy  must  result.  When  the  steam  is 
admitted  to  the  steam  cylinder  for  the  full  stroke,  it  is  evident  that 
no  economy  can  result  from  the  use  of  higher  pressures,  and,  in  fact, 
the  higher  pressure  must  lead  to  increased  coal  consumption ;  but  if 
the  steam  can  be  employed  expansively,  as  by  cutting  it  off  at  a  small 
portion  of  the  stroke,  a  considerable  economy  is  obtained.  Thus, 
from  the  table  of  Mean  Pressures,  it  will  be  seen  that  with  a  gauge 
pressure  of  105  Ibs.  per  square  inch,  and  with  a  cut-off  at  ^  of  the 
stroke,  the  mean  pressure  behind  the  piston  is  39'64  Ibs.  per  square 
inch,  or  practically  the  same  as  would  have  been  obtained  if  the 
steam  had  been  allowed  to  enter  the  cylinder  during  the  whole  of  the 
stroke  with  an  initial  pressure  of  40  Ibs..  while  only  -jJ0-  part  of 
the  steam  is  employed. 

But  with  the  use  of  higher  and  higher  pressures,  a  difficulty 
arises,  owing  to  what  is  known  as  cylinder  condensation.  It  will  be 
remembered  that  the  temperature  of  the  steam  varies  with  the  pres- 
sure. Thus,  taking  the  case  just  quoted,  that  of  steam  at  105  Ibs. 


216    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


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THE  STEAM   ENGINE  217 

initial  pressure,  with  a  cut-off  at  ^  of  the  stroke,  the  temperature 
of  the  steam  at  that  pressure  is  341°  F.  Assuming  the  final  pressure 
of  the  steam  to  be  about  that  of  the  atmosphere,  the  temperature  is 
only  212°.  The  cylinder  walls  naturally  follow  these  changes,  cool- 
ing as  the  steam  expands,  and  its  temperature  lowers,  warming  up 
again  with  the  fresh  steam  that  enters  on  the  following  stroke. 
Further,  it  will  be  remembered,  where  the  engine  is  working  with  a 
condenser,  the  temperature  of  the  steam  in  front  of  the  piston  may 
be  as  low  as  about  100°  F.,  and  the  cylinder  walls  and  the  cylinder 
cover  at  that  end  will  follow  this  temperature,  as  explained.  This 
means  that  the  cylinder  cover  and  the  portion  of  the  cylinder  walls 
at  that  end,  where  the  fresh  steam  is  to  enter,  will  have  been  exposed 
to  a  temperature  of  only,  say,  100°,  just  previously  to  the  entrance  of 
steam  at  341°.  It  has  been  pointed  out,  in  dealing  with  the  question 
of  superheating,  and  in  discussing  the  properties  of  steam  in  Chapter 
I.,  that  the  steam  contains  a  quantity  of  vapour,  unless  it  has  been 
superheated,  and  the  effect  of  the  impingement  of  the  steam  upon  the 
comparatively  cool  surfaces  in  the  cylinder  into  which  it  enters  is, 
the  condensation  of  this  vapour,  and  also  sometimes  the  lowering  of 
the  temperature  of  the  whole  body  of  the  steam,  certainly  of  all  of 
it  which  comes  into  contact  with  the  metal  surfaces  of  the  cylinder, 
these  actions  leading  to  loss  of  heat,  which  has  to  be  made  up  in  the 
furnace  of  the  boiler  later  on.  The  vapour  which  is  condensed  upon 
the  inner  surface  of  the  cylinder  is  reformed  into  steam  at  a  later 
portion  of  the  stroke,  when  these  surfaces  have  been  warmed  up  at 
the  expense  of  the  entering  steam,  the  conversion  of  the  condensed 
vapour  into  steam  absorbing  a  considerable  quantity  of  heat  from 
the  cylinder  walls  and  cover,  and  tending  to  lower  their  temperature 
towards  the  end  of  the  stroke,  in  addition  to  the  lowering  which  takes 
place  from  the  expansion  of  the  steam.  This  difficulty  has  been  met 
in  three  ways. 

(1)  By  superheating  the  steam  so  that  it  carries  no  watery  vapour 
on  entering  the  cylinder,  and  that  it  also  carries  a  sufficient  excess  of 
heat  to  raise  the  temperature  of  the  cylinder  walls  without  lowering 
its  own  temperature  below  that  at  which  it  left  the  boiler. 

(2)  By  fitting  the  cylinders  with  jackets,  through  which  live 
steam  is  passed,  either  on  its  way  into  the  cylinder,  or  by  a  special 
jet,  which  is  allowed  to  condense  and  is  drained  off. 

(3)  By  dividing  up  the  range  of  expansion  over  several  cylinders, 
the  engines  so  constructed  being  known  as  compound,  triple  expansion, 
and  quadruple  expansion  engines. 

Superheating  has  already  been  dealt  with.  The  question  of  steam 
jackets  will  be  dealt  with  later  on,  and  also  the  construction  and 
working  of  compound,  triple,  and  quadruple-expansion  engines. 

Meanwhile,    it    may    be    noted    that,    provided    that    cylinder 


218     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

condensation  can  be  got  rid  of,  considerable  economies  are  obtainable 
by  the  use  of  higher  steam  pressures  in  single  cylinders,  and  that 
cylinders  of  a  certain  size  may  be  made  to  do  more  work  by  using 
higher  steam  pressures  than  they  would  have  with  lower  pressures. 


The  Work  a  Steam  Engine  will  Perform 

The  work  a  steam  engine  will  perform  depends  directly  upon  the 
sectional  area  of  the  cylinder,  upon  the  mean  effective  steam  pressure 
working  upon  the  piston,  and  upon  the  distance  the  piston  travels 
in  a  given  time.  It  will  be  remembered  that  1  H.P.  represents 
33,000  foot  Ibs.,  and  the  work  that  steam  cylinders  are  capable  of 
performing  is  measured  in  H.P.,  the  number  of  foot  pounds  being 
obtained  by  the  formula  — 


33,000 

Where  H.P.  is  the  horse-power  the  cylinder  will  furnish,  P  is  the 
mean  effective  pressure  exerted  on  the  piston,  L  is  the  length  of  the 
stroke  of  the  piston  in  feet,  the  distance  over  which  it  travels  when 
moving  from  one  end  of  the  cylinder  to  the  other,  and  N  is  the  number 
of  revolutions  of  the  crank  shaft,  or  of  double  strokes  of  the  engine 
per  minute.  A  is  the  area  of  the  piston  in  square  inches. 

The  mean  effective  pressure  is  the  mean  pressure  behind  the 
piston,  less  the  mean  pressure  in  front  of  the  piston.  It  has  been 
explained  that  on  the  return  stroke  the  piston  has  to  drive  out  the 
steam  from  the  cylinder  that  was  employed  in  pushing  the  piston  on 
the  previous  stroke.  If  the  engine  exhausts  only  to  the  atmosphere, 
the  back  pressure,  as  it  is  called  —  the  pressure  in  front  of  the  piston  — 
will  be  that  of  the  atmosphere,  plus  that  remaining  in  the  steam,  and 
will  be  gradually  decreasing  as  the  piston  reaches  the  end  of  the 
stroke.  Whatever  the  mean  of  all  the  back  pressure  is,  that  has  to 
be  subtracted  from  the  mean  of  all  the  pressures  in  front  of  the 
piston,  and  the  result  is  the  figure  to  be  employed  in  the  formula 
given  above.  This  pressure,  when  multiplied  by  the  number  of 
square  inches  in  the  surface  of  the  piston  that  is  exposed  to  the  steam 
pressure,  gives  the  total  pressure  acting  upon  the  piston  —  that  is  the 
total  average  pressure  throughout  the  stroke  ;  and  this  multiplied  by 
the  distance  through  which  the  piston  travels  in  a  minute,  gives  the 
number  of  foot  pounds  of  work  done  by  the  piston.  Thus,  taking  a 
piston  having  a  diameter  of  12  inches,  its  area  will  be  113  square 
inches,  and  if  the  mean  effective  pressure  was,  say,  40  Ibs.,  the  total 
pressure  acting  upon  the  piston  is  4520  Ibs.  If  the  stroke  of  the 
engine  is  12  inches,  and  it  runs  at  300  revolutions,  or  300  double 


THE   STEAM   ENGINE  219 

strokes  per  minute,  the  travel  will  be  600  feet  per  minute,  and 
the  total  work  done  in  foot  pounds  will  be  2,712,000,  or  about  82  H.P., 
as  follows — 

40  x  113  x  2  x  1  x  300 
H'R  =  33,000~  H'R 

A  point  that  perhaps  may  be  as  well  mentioned  here  is,  the  steam 
cylinder  is  often  fixed  in  a  horizontal  position,  and  even  when  it  is 
fixed  vertically,  only  one  of  the  strokes  is  lifting,  while  we  under- 
stand the  rate  of  doing  work  as  so  many  pounds  lifted  so  many  feet 
per  minute.  The  explanation  is,  though  the  engine  may  be  fixed 
horizontally,  the  motion  of  its  piston  is  communicated  to  a  crank 
shaft,  or  may  be,  and  if  a  pulley  be  fixed  upon  the  end  of  the  shaft, 
and  a  rope  be  arranged  to  wind  up  on  the  pulley,  the  end  of  the  rope 
being  carried  over  a  pulley  at  any  given  height  and  attached  to  a 
weight  on  the  ground,  or  below  the  ground,  it  will  do  work  in  lifting 
the  weight,  just  as  if  the  power  had  been  applied  directly,  the  work 
done  upon  the  weight  being  that  delivered  by  the  piston,  less  the 
charges  for  friction,  etc. 


Indicated  Horse=power  and  Brake  Horse-power 

Another  point  that  had  also  better  be  explained,  is  what  is  meant  by 
"  indicated  "horse-power,  as  distinguished  from  "  brake  "  horse-power, 
and  again  from  "  nominal "  horse-power.  By  indicated  horse-power  is 
meant  the  total  power,  or  work,  that  the  piston  will  perform,  taking  the 
horse-power  at  33,000  foot  Ibs.  per  minute,  or  550  foot  Ibs  per  second, 
and  it  is  found  by  the  use  of  the  formula  given  above  for  horse-power, 
the  mean  effective  pressure  being  found  by  means  of  an  apparatus 
called  the  indicator.  It  has  been  mentioned  that  the  steam  pressure 
falls  gradually  as  the  steam  expands,  after  the  entry  port  is  closed, 
and  that  the  pressure  in  front  of  the  piston  also  falls  gradually  as  the 
steam  escapes.  A  little  apparatus,  to  be  described  later,  is  arranged 
to  measure  this  fall  on  each  side  of  the  piston,  exactly  as  it  takes 
place.  The  indicator  draws  a  curved  line  upon  a  paper  provided 
for  the  purpose,  rolled  on  a  cylinder,  the  height  of  the  curved  line 
above  the  horizontal  line  measures  the  steam  pressure  at  each  portion 
of  the  stroke,  and  the  mean  is  taken  of  all  of  these  lines,  this  being 
the  mean  pressure  behind  the  piston.  The  same  thing  is  done  for 
the  mean  pressure  in  front  of  the  piston,  and  the  one  is  subtracted 
from  the  other.  In  some  cases  the  two  sets  of  pressure  are  taken 
on  the  same  diagram,  and  they  are  then  easily  subtracted  one  from 
the  other. 

By  "  brake  "  horse-power,  or  as  it  is  sometimes  expressed,  "  actual  " 


220    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

horse-power,  is  meant  the  power  that  is  actually  available,  or  the 
work  that  can  be  actually  done  by  the  crank  shaft  of  the  engine,  to 
which  the  piston  delivers  its  power,  and  it  is  found  by  actual  measure- 
ment, by  a  brake  designed  specially  for  the  purpose,  to  absorb  the 
power  that  is  being  measured,  and  it  equals  the  indicated  horse-power, 
less  the  power  absorbed  by  the  engine  itself  in  friction,  etc. 

"  Indicated  "  horse-power  is  not  often  referred  to  now,  as  engines 
vary  very  much  in  their  efficiency. 

The  efficiency  of  the  engine  is  the  brake  horse-power,  divided  by 
the  indicated  horse-power,  and  may  range  from  80  up  to  95  per  cent. 
In  small  engines,  and  in  engines  where  lubrication  is  not  properly 
attended  to,  or  that  are  allowed  to  get  dirty,  the  efficiency  may  be 
considerably  lower  than  this ;  but  large  well-made  engines  should 
always  give  as  much  as  90  per  cent,  efficiency. 

Where  there  is  more  than  one  cylinder,  as  in  double  cylinder 
engines,  and  in  compound,  triple  expansion  engines,  etc.,  each  cylinder 
is  indicated  by  itself,  and  the  total  indicated  horse-power  of  the  engine 
is  the  sum  of  the  horse-powers  of  each  cylinder,  using  the  indicated 
effective  mean  pressure  in  each. 

"  Nominal "  horse-power  is  a  term  rapidly  going  out  of  use.  It 
has  no  real  meaning.  It  was  a  term  adopted  in  the  very  early  days 
of  steam-engine  work,  by  different  makers,  as  a  rough  guide  of  what 
an  engine  would  do.  The  indicated  horse-power  of  an  engine  is 
very  often  from  four  to  six  times  the  nominal  horse-power. 


Double-Cylinder  Engines 

Double- cylinder,  or  twin-cylinder,  engines  are  not  so  common  now 
as  they  were  some  years  ago,  because,  with  the  increase  of  steam 
pressures,  the  second  cylinder  is  now  usually  arranged  on  the  com- 
pound principle.  The  twin- cylinder  engine  forms  a  very  convenient 
arrangement  for  putting  double  the  power  within  a  small  space,  and 
for  obtaining  a  more  even  turning  moment  on  the  crank  shaft.  It 
will  be  understood  that  the  pressure  upon  the  piston,  varying  as  it 
does,  as  described,  the  turning  effort  conveyed  by  the  piston  to  the 
crank  shaft  will  also  vary,  and  that  with  a  single  cylinder  there  will 
be  a  considerable  variation,  particularly  where  the  engine  is  working 
very  expansively,  between  the  entrance  of  the  steam  and  the  end  of 
the  stroke.  With  two  cylinders,  having  their  crank  shafts  fixed 
either  90°  or  180°  apart,  this  difference  is  lessened ;  and,  as  will  be 
seen  with  larger  engines  working  very  expansively,  it  is  arranged  to 
distribute  the  turning  effort  more  and  more  evenly  round  the  circle 
in  which  the  crank  shaft  moves  by  increasing  the  number  of  cylinders, 
and  by  arranging  the  cranks  evenly  round  the  circle.  • 


THE  STEAM   ENGINE 


221 


Compound   Engines 

The  compound  engine,  as  mentioned  above,  consists  of  two 
cylinders,  through  which  the  steam  passes  in  succession,  the  cylinders 
being  known  as  the  high  pressure  (H.P.)  and  the  low  pressure  (L.P.). 
The  two  cylinders  are  arranged  to  deliver  their  power  to  the  same 
crank  shaft,  sometimes  by  being  fixed  side  by  side  and  having  two 
cranks  arranged  either  90°  or  180°  apart,  and  sometimes,  particularly 
with  the  high-speed  engines  to  be  described,  the  two  cylinders  are 


(L 


TO   /JTMOSPHEftL 


£X/f/7l/-ST 

FIG.  86. — Diagram  showing  the  course  of  the  Steam,  with  a  Non-condensing  Simple 
Engine,  from  the  Boiler  to  the  Atmosphere. 

placed  one  above  the  other,  the  same  piston  rod  carrying  the  two 
pistons,  and  passing  through  the  two  cylinders.  The  two  cylinders 
are  always  arranged  to  perform  exactly  the  same  work,  that  is  to 
say,  to  furnish  exactly,  or  as  nearly  as  possible,  the  same  amount  of 


STEfJM    PIPE. 


BO/LER 


FIG.  87. — Diagram  showing  the  course  of  the  Steam,  in  a  Non-condensing  Compound 
Engine,  between  the  Boiler  and  the  Atmosphere. 

energy.  This  means  that  the  diameter  of  the  low-pressure  cylinder 
is  larger  than  that  of  the  high-pressure  cylinder,  because  as  the 
stroke  of  the  two  pistons  must  be  exactly  the  same,  and  the  pressure 
at  which  the  steam  is  delivered  to  the  low-pressure  cylinder  is  con- 
siderably less  than  that  at  which  it  is  delivered  to  the  high-pressure 
cylinder,  the  only  way  in  which  the  work  done  by  the  low-pressure 
can  be  made  equal  to  that  done  by  the  high-pressure  cylinder,  is  by 


222    STEAM   BOILERS,   ENGINES,  AND   TURBINES 

increasing  the  area  of  the  piston.  THe  same  formula  applies,  but  as 
the  length  and  number  of  strokes  are  the  same,  the  total  pressure  is 
made  the  same  by  increasing  the  area.  The  proportion  between  the 
cylinders  varies  with  the  conditions  under  which  the  expansion  is 


FIG.  88. — Single-cylinder  Wall  Engine,  made  by  Bansome,  Sims,  and  Jeffries.     The 
bracket  shown,  bolted  to  the  wall,  supports  the  Engine. 

carried  out  between  1  for  the  high-pressure  and  2 \  to  4J  for  the  low- 
pressure. 

It  will  be  understood  that  the  steam  passes  first  into  the  high- 
pressure  cylinder,  and  from  its  exhaust  valve  to  a  receiver,  and 
thence  to  the  entry  valve  of  the  low-pressure,  passing  from  the 


THE   STEAM   ENGINE 


223 


FIG.  89. — Single-cylinder  Horizontal  Engine,  mounted  with  Vertical  Boiler,  made 

by  H.  Coltman  &  Sons. 


FIG.  90. — Longitudinal  Section  of  a  Tandem  Compound  Engine,  without  Receiver 
between.    The  high  pressure  is  the  rear  Cylinder. 


224    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

exhaust  valve  of  the  low-pressure  either  to  the  atmosphere,  or  to 
the  condenser.  It  is  very  common  now  for  the  exhaust  steam  from 
the  high-pressure  cylinder  to  be  reheated  on  its  way  to  the  low- 
pressure  cylinder,  the  object  being  the  same  as  that  sought  to  be 


FIG.  91. — Horizontal  Tandem  Compound  Condensing  Engine,  made  by  E.  B.  and 
F.  Turner.  The  Condenser  is  mounted  on  the  same  Bed-plate  as  the  Engine, 
and  the  Air-pump  is  worked  from  the  Tail  Shaft.  The  High-pressure  Cylinder  is 
in  front  in  this  case. 

attained  by  superheating  the  steam,  the  prevention  of  the  formation 
of  vapour,  and  its  condensation  on  the  walls  of  the  low-pressure 
cylinder. 

Eeheaters  are  of  various  forms,  but  mainly  on  the  lines  of  the 
feed-water  heater.     In  the  reheater,  the  steam  passing  to  the  low- 


1     ,*.%i~--- 


FiG.  92. — Horizontal  Cross-compound  Condensing  Engine,  made  by  Ransome, 
Sims  &  Co.  The  Condenser  is  mounted  separately,  and  its  Air-pump  driven 
from  the  Tail  Shaft. 

pressure  cylinder  is  carried  through  tubes,  and  a  certain  quantity 
of  live  steam  through  the  space  surrounding  them.  The  reheater 
forms  the  receiver  between  the  high-  and  '  low-pressure  cylinders. 
The  receiver  between  the  two  cylinders  is  the  source  of  steam 


PLATE  13A. — Galloway's  Vertical  Cross  Compound  Engine. 


PLATE   13B.—  Marshall' 


Horizontal  Coupled  Compound   Condensing  Engine,  with 
Slide  Valves. 


'LATE     13c. — Marshall's   Horizontal   Tandem    Compound   Engine,   with   Trip-gear 

Valves.  [To  face  p.  224. 


THE   STEAM   ENGINE 


225 


for  the  low-pressure  cylinder,  just  as  the  boiler,  or  steam  range,  is 
for  the  high-pressure.  Figs.  86  and  87  show,  diagrammatically,  the 
course  of  the  steam,  from  the  boiler  to  the  atmosphere,  with  simple 
and  compound  engines.  Where  condensers  are  employed,  the  steam 


FIG.  93.— Compound  Vertical  Engine,  unenclosed,  with  Shaft  Governor. 

)asses  from  the  low-pressure  cylinder  to  the  condenser,  instead  of 
o  the  atmosphere.  Figs.  88  and  89,  and  Plates  10B,  lOc,  and  10D, 
re  examples  of  simple  engines  of  ordinary  type,  Figs.  90,  91,  92,  and 
j)3,  and  Plates  HA,  HB,  and  He,  13A,  13B,  and  13c,  and  14A  and 
4fi,  show  various  forms  of  compound  engines, 

Q 


226    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


Triple- Expansion   Engines 

The  triple-expansion  engine  may  have  three  or  four  cylinders, 
known  respectively  as  the  high  pressure  (H.P.),  the  intermediate 
pressure  (I.P.),  and  the  low  pressure  (L.P.). 

The  low  pressure  is  sometimes  divided  into  two,  the  steam  passing 
first  to  the  high-pressure  cylinder,  then  to  the  intermediate  pressure, 
and  then  dividing  between  the  two  low-pressure  cylinders.  The 
reason  of  this  arrangement  is,  in  the  case  of  the  very  high  pressures 
that  are  used,  in  large  steamships,  for  instance,  and  the  large  amount 
of  power  required,  the  low-pressure  cylinder  would  be  very  large  if 
arranged  as  a  single  cylinder;  and,  in  addition,  the  fourth  cylinder 


ZX/MUST 


FIG.  94. — Diagram  of  the  course  of  the  Steam  in  a  Non-condensing  Triple  Expansion 
Engine,  from  the  Boiler  to  the  Atmosphere. 

gives  another  crank  on  the  propeller  shaft,  and  tends  to  give  a  more 
even  turning  moment. 

The  three  cylinders,  or  the  three  sets  of  cylinders,  must  conform 
to  the  same  rules  as  the  two  cylinders  in  the  case  of  the  compound 
engine.  The  high  pressure,  the  intermediate  pressure,  and  the  low 
pressure,  whether  the  last  be  of  one  or  two  cylinders,  must  furnish 
exactly  the  same  horse-power.  The  horse-power  furnished  by  each 
cylinder,  or  set  of  cylinders,  should  be  that  delivered  to  the  crank 
shaft,  as  it  will  be  evident  that  the  friction  of  the  different  cylinders 
will  not  be  the  same. 

The  three  cylinders,  or  sets  of  cylinders,  are  arranged  in  different 
ways.  For  ocean  steamships,  whether  there  are  three  or  four 
cylinders,  they  usually  stand  side  by  side,  vertically  above  the  crank 
shaft,  to  which  each  of  their  pistons  is  connected.  Plate  15A  shows 


THE   STEAM    ENGINE  227 

one  of  these  made  by  the  Central  Engineering  Works.  In  high- 
speed engines  employed  on  land  work,  and  particularly  in  those 
forms  used  for  driving  electricity  generators,  various  arrangements 
rule.  In  some  cases  the  three  cylinders  are  fixed  one  above  the 
other,  one  piston  rod  answering  for  the  three,  and  one  crank  shaft. 
In  those  cases  it  is  not  inncommon  for  the  work  the  engine  is  to  do 
to  be  split  up  between  two  or  more  sets  of  cylinders,  so  as  to  have 
two  or  more  cranks.  The  arrangement  of  cylinders  vertically  one 
above  the  other  is  convenient  for  manufacturing  purposes,  since  a 
simple  engine  becomes  a  compound  engine  by  fixing  an  additional 
cylinder  above,  and  a  compound  engine  becomes  a  triple-expansion 
engine  by  fixing  a  third  smaller  cylinder  above  the  other  two. 
Keceivers  are  used  between  the  high- pressure  and  intermediate- 
pressure  cylinders,  and  between  the  intermediate-pressure  and  low- 
pressure,  and  reheating  is  carried  out  in  various  ways. 

Quadruple- Expansion   Engines 

Quadruple-expansion  engines  may  consist  of  four,  five,  or  six 
cylinders.  In  fact,  there  is  no  reason  that  both  of  the  two  lower- 
pressure  cylinders  should  not  be  divided  up  as  convenient.  They 
are  known  as  high  pressure  (H.P.),  first  intermediate  (First  I, P.), 
second  intermediate  (Second  I.P.),  and  low  pressure  (L.P).  Quadruple- 
expansion  engines  are  only  employed,  so  far  as  the  author  is  aware, 
in  ocean  steamships.  The  same  rules  with  regard  to  the  power 
delivered  by  each  cylinder,  or  set  of  cylinders,  apply  that  have 
been  mentioned  for  compound  and  triple-expansion  engines,  and  the 
same  arrangements  are  employed  for  receiving  and  reheating  the 
steam  between  the  different  cylinders. 

The  four,  five,  or  six  cylinders  are  usually  arranged  side  by  side, 
vertically  over  the  crank  shaft. 

High-   and   Low-Speed   Engines 

By  "high-speed  engines"  are  understood  those  which  make  a 
large  number  of  revolutions  per  minute,  300  and  upwards;  while 
"  low-speed  engines  "  are  understood  to  be  those  which  make  a  small 
number,  100  and  under,  per  minute.  There  is  an  intermediate  class 
of  engines  that  have  speeds  ranging  from  150  to  250  revolutions 
per  minute,  of  which  the  engine  shown  in  Fig.  93  is  an  example. 
The  names  are  really  incorrect.  The  proper  classification  of  engines, 
so  far  as  speed  is  concerned,  is  by  the  speed  of  the  piston.  Twenty- 
five  and  thirty  years  ago,  300  feet  per  minute  was  taken  as  the 
standard  piston  speed,  and  conservative  engineers  preferred  a  speed 


228     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

a  little  less.  To-day,  600  feet  per  minute  is  a  fair  standard,  though 
some  very  large  engines  are  run  at  lower  speeds.  It  will  be  evident 
that  the  piston  speed  will  be  the  same,  of  an  engine  running,  say,  at 
400  revolutions  per  minute,  if  its  stroke  is  9  inches,  and  that  of  an 
engine  running  at  100  revolutions  per  minute,  if  its  stroke  is  3  feet. 
The  term  "quickly-revolving  engines,"  was  introduced  by  the  late 
Mr.  Morcom,  of  Belliss  and  Morcom,  some  years  ago,  but  it  does  not 
appear  to  have  been  taken  up,  and  the  terms  "  high  speed  "  and  "  low 
speed  "  are  still  used,  the  term  "  high  speed  "  meaning  those  engines 
which  have  a  short  stroke  and  a  large  number  of  revolutions  per 
minute;  and  "low  speed,"  those  which  have  a  long  stroke  and  a 
small  number  of  revolutions  per  minute. 

Examined  from  another  point  of  view,  also,  the  terms  appear  to 
be  wrong,  because  while  the  piston  speeds  may  be  the  same,  the 
peripheral  speeds  of  the  flywheels  of  the  so-called  slow-running 
engines  are  often  very  much  higher  than  those  of  the  flywheels  of 
the  so-called  high-speed  engines. 

The  high-speed  engine,  to  use  the  term  commonly  employed,  is 
gradually  making  its  way,  though  the  engineers  who  have  been 
developing  it  have  had  a  great  many  difficulties  in  their  way.  Old 
engineers  viewed  with  great  concern  the  apparently  quickly  moving, 
parts  of  the  high-speed  engine,  and  it  may  be  stated  that  their  con- 
cern was  quite  justified,  as  some  of  the  early  engines  did  as  prophesied 
for  them,  and  knocked  themselves  to  pieces.  The  main '  difficulty 
was,  however,  that  of  lubrication,  and  this  has  now  been  completely 
overcome  by  the  systems  of  splash  lubrication  adopted  in  the  Willans 
and  other  engines,  and  the  forced  lubrication  adopted  in  the  Belliss  and 
others.  The  high-speed  engines  are  always  enclosed,  that  is  to  say, 
their  crank  shafts,  piston  rods,  etc.,  are  enclosed  inside  a  casing,  in 
which  the  lubricating  arrangements  are  carried  on.  The  casing 
provides  a  chamber  in  the  case  of  the  splash  lubricating  methods  for 
the  lubricant,  and  it  is  also  found  convenient  with  the  other  forms  of 
lubrication.  The  intermediate  speed  engines  are  not  enclosed. 

By  splash  lubrication  is  meant,  the  crank  shaft  runs  in  a  fluid 
formed  of  a  lubricant  mixed  with  water,  and,  as  it  turns  round,  it 
churns  the  mixture  up,  throwing  it  over  all  parts  of  the  crank  shaft, 
piston  rod,  etc.,  and  keeping  everything  fairly  cool.  One  of  the 
reasons,  it  will  be  easily  understood,  for  enclosing  the  space  in  which 
the  crank  shaft,  the  piston; rod,  etc.,  work,  where  splash  lubrication 
is  employed,  is  to  prevent  the  lubricant  from  being  thrown  all  over 
the  engine-house,  and  this  applies  more  or  less  to  all  forms  of  high- 
speed engine. 

There  are  several  forms  of  high-speed  engines  on  the  market,  all 
of  them  having  certain  parts  common.  In  all  there  is  the  enclosure 
of  the  crank  shaft  mentioned,  with  doors  on  both  sides  provided  for 


THE  STEAM  ENGINE 


229 


examination  and  repair  of  the  machinery  inside,  the  enclosures  being 
constructed  in  various  ways.  Messrs.  W.  H.  Allen  &  Co.  call  their 
enclosure  a  cast-iron  trunk.  The  cylinders,  which  are  always  above 
the  crank  shafts,  are  supported  from  the  top  of  the  enclosed  space  by 
distance  pieces,  usually  of  cast  iron,  which  also,  in  some  forms,  act  as 
guides  for  the  piston  cross  heads.  Fig.  95  shows  longitudinal  and 
transverse  sections  of  a  compound  enclosed  engine,  made  by  this 
firm.  Fig.  96  shows  a  compound  enclosed  Belliss  engine,  and  Fig. 
97  a  compound  enclosed  Browett-Lindley.  The  Willans  engine 
differs  from  the  other  high-speed  engines  in  this  respect,  that  it 
is  completely  enclosed  from  the  top  to  the  bottom. 

In  the  double-acting  high-speed  engines  made  by  Messrs.  Belliss 


FIG.  95. — Longitudinal  and  Transverse  Sections  of  Allen's  Enclosed  High-speed 

Engines. 

&  Morcom,  W.  H.  Allen  &  Son,  Browett  &  Lindley,  Brotherhood, 
and  others,  the  valves  providing  for  the  entry  and  egress  of  steam 
to  and  from  the  cylinder,  are  of  the  piston  slide-valve  type,  or,  as 
they  are  usually  called,  the  piston  type.  In  the  Belliss  engine, 
with  compound  engines,  one  piston  valve,  worked  by  one  eccentric, 
distributes  the  steam  to  the  two  cylinders,  the  cranks  of  the  two 
engines  being  arranged  180°  apart,  so  that  steam  is  entering  one 
cylinder  above  the  piston,  and  the  other  cylinder  below  the  piston ; 
this,  it  is  claimed,  tending  to  balance  the  strains  upon  the  crank 
shaft,  bearings,  etc.  With  triple-expansion  Belliss  engines,  there 
are  two  eccentrics  and  two  piston  valves,  one  supplying  steam 
to  the  intermediate  and  low-pressure  cylinders,  and  the  other  sup- 
plying steam  to  the  high-pressure  cylinder. 


230    STEAM  BOILERS,  ENGINES,  AND  TURBINES 


FIG,  96. — Transverse  and  Vertical  Section  of  a  Compound  Bell  is 

Engine. 


igh-speed  Enclosed 


FIG.  97. Longitudinal  and  Transverse  Section  of  a  Browett-Lindley  Compound, 

High-speed  Enclosed  Engine. 


THE  STEAM  ENGINE  131 

In  the  Allen,  the  Browett,  and  the  Brotherhood  engines,  piston 
valves  are  also  employed,  but  there  is  one  to  each  cylinder,  and  an 
eccentric  to  each  valve. 

In  all  of  the  double-acting  high-speed  engines  mentioned,  the 
bottom  of  the  crank  case  is  used  as  a  reservoir  for  the  oil  into  which 
it  drains,  after  having  been  forced  through  the  different  bearings, 
etc.,  and  it  is  taken  from  this  reservoir  by  means  of  a  valveless 
pump,  the  suction  of  the  pump  being  protected  by  a  strainer  from 
any  matter  that  may  have  got  into  the  crank  chamber.  In  the 
Belliss  engine  the  oil  pump  is  of  the  oscillating  type,  the  oscillations 
enabling  the  apparatus  to  be  worked  without  valves,  that  require  to  be 
opened  and  closed  mechanically,  etc.  In  all  of  them  also  the  piston 
rods,  connecting  rods,  etc.,  are  provided  with  oil  scrapers,  intended 
to  throw  the  oil  from  the  rods  down  into  the  crank  chamber.  Any 
water  that  is  formed  in  the  cylinders  also  is  allowed  to  drain  into 
the  crank  chamber,  and  is  removed  from  time  to  time. 

The  cylinders  of  high-speed  engines  are  made  of  close-grained 
cast  iron,  machined  all  over.  In  the  Brotherhood  the  iron  is  cast 
from  selected  scrap  and  cold  blast  pig,  and  the  surfaces  are  strongly 
ribbed.  The  pistons  are  usually  of  cast  iron.  In  the  Brotherhood 
they  are  made  of  forged  steel,  with  packing  rings  of  hard  cast  iron.  In 
the  Browett  the  high-pressure  piston  is  of  cast  iron,  the  intermediate 
and  low  pressure  pistons  of  pressed  steel  with  packing  rings.  The 
piston  valves  are  usually  of  cast  iron,  with  special  packing  rings. 

All  of  the  double-acting  high-speed  engines  mentioned  are  con- 
trolled by  throttle  governors,  worked  from  the  crank  shaft,  the  valve 
itself  being  moved  by  vertical  rods,  as  shown  in  the  drawings,  leading 
up  from  the  governor.  The  governors  are  of  various  forms,  the  two 
balls  revolving  on  a  spindle  being  a  favourite  one ;  but  in  the  case  of 
the  Browett,  the  governor  is  carried  on  a  disc,  the  governor  balls  being 
carried  by  arms  pivotted  on  the  disc.  In  all  of  the  engines  mentioned, 
the  working  parts  of  the  governor  are  supplied  with  forced  lubri- 
cation from  the  same  supply  as  the  bearings  and  other  parts  of  the 
engine. 

The  question  of  the  lubricant  is  a  very  important  one  in  high- 
speed engines,  and  all  of  the  makers  recommend  that  a  high  class 
mineral  oil  should  be  employed.  Messrs.  Allen  recommend  that  dry 
steam  should  be  employed,  and  that  superheating  from  50°  to  150°  F. 
is  an  advantage ;  but  they  point  out  that  with  dry  steam,  it  is  necessary 
to  supply  additional  internal  lubrication  to  the  cylinder,  because  the 
moisture  contained  in  the  ordinary  saturated  boiler  steam  acts  as  a 
lubricant. 


STEAM   BOILERS,  ENGINES,   AND   TURBINES 


The  Ernest  Scott  and  Mountain  High-speed 

Engine 

Messrs.  Ernest  Scott  &  Mountain  make  two  forms  of  engines, 
enclosed  and  non-enclosed,  the  enclosed  engines,  as  explained,  running 
at  a  higher  speed  than  the  non-enclosed. 

The  enclosed  engines  are  made  with  two  and  three  cranks,  simple 
engines  being  made  with  two  equal  cylinders,  compound  engines 
with  the  usual  differential  cylinders,  and  three-crank  compound 
engines  being  made  with  one  high-pressure,  and  two  low-pressure 
cylinders,  the  high-pressure  cylinder  being  in  the  middle.  A  special 
feature  of  the  engine  is,  the  central  valve  that  is  employed  to  con- 
trol the  steam  admission  to  the  two  cylinders,  where  two  are 
emploped,  whether  compound  or  simple.  The  steam-distributing 
valves  are  of  the  piston  type,  with  the  usual  entrances  to  the  steam 
cylinders,  similar  to  those  of  the  slide  valve,  one  eccentric  controlling 
the  admission  of  steam  to  and  the  exit  from  both  cylinders,  by  the 
position  of  the  two  piston  valves.  The  piston  valves  are  fitted  with 
piston  rings,  with  renewable  cast-iron  liners,  claimed  to  ensure  accurate 
opening  and  closing  of  the  steam  ports,  and  allowing  for  alteration 
of  the  cut-off  if  necessary. 

The  .cylinders  are  supported  from  the  crank  case  by  the  usual 
distance  pieces,  and  the  lubrication  of  all  the  parts  is  by  oil  under 
pressure,  delivered  by  one  or  two  pumps,  at  an  approximate  pressure 
of  20  Ibs.  per  square  inch. 


The  Willans  Central  Valve  Engine 

In  the  Willans  engine,  which  was  one  of  the  earliest  of  the  high- 
speed engines  to  do  really  practical  work,  the  late  Mr.  Willans,  having 
carried  out  numerous  experiments  upon  the  working  of  steam  in 
high-speed  engines,  a  very  special  arrangement  of  valves  rules,  the 
piston  rod  performing  the  double  office  of  carrying  the  power  from 
the  pistons  to  the  crank  shaft,  and  also  of  carrying  the  steam  into, 
the  different  cylinders.  The  cylinders  are  arranged  vertically  above 
the  crank  shaft,  and  the  crank  shaft  works  in  an  enclosed  crank 
chamber,  as  described  on  page  228,  partially  filled  with  a  lubricant, 
the  lubricant  usually  consisting  of  oil  and  water,  and  the  crank  shaft, 
as  it  moves  round,  splashing  the  liquid  up  upon  the  different  parts 
of  the  apparatus.  The  steam  chest  communicates  with  the  space  at 
the  top  of  each  cylinder.  As  mentioned,  the  piston  rod  performs 
the  office  of  distributing  the  steam,  and  in  order  to  enable  it  to  do 
so,  it  is  made  in  the  form  of  a  tube  or  trunk.  There  is  a  rod 


PLATE  14A. — Another  View  of  Engine  shown  in  Plate  HA. 


PLATE  14s. — Marshall's  Coupled  Compound  Condensing  Engine,  driving  a  Dynamo 
by  Eopes  ;  the  Cylinders  have  Trip  Valve  Gear.       [To  face  p.  232. 


THE   STEAM   ENGINE  233 

inside  of  the  hollow  piston  trunk,  carrying  rings.  These  are  the 
valves,  and  both  the  piston  rod  and  the  valve  rod  move,  so  that 
the  positions  of  the  valves  change  with  reference  to  the  ports  in  the 
piston  trunk.  The  valve  rod  is  moved  by  an  eccentric,  attached  to, 
and  worked  by  the  crank,  the  end  of  the  valve  rod  being  secured  to 
the  crank-pin.  The  motion  of  the  eccentric  and  of  the  piston  give 
the  requisite  variation  between  the  positions  of  the  valves,  relatively 
to  the  ports  in  the  hollow  piston  trunk.  The  piston  trunk  itself 
ends  in  a1  guide  piston,  working  inside  an  air  chamber,  formed  by 
a  cylinder  closed  at  the  top,  the  piston  trunk  passing  through  an 
aperture  provided  for  it  in  the  top.  When  the  steam  is  first 
admitted  to  either  engine  it  passes  into  the  cylinder  by  way  of  the 
hollow  piston  trunk,  when  the  ports  are  uncovered.  Thus,  when 
certain  ports  marked  are  uncovered,  steam  passes  from  the  steam 
chest  into  the  piston  trunk,  and  when  other  ports  are  uncovered,  the 
steam  passes  out  of  the  piston  trunk  into  the  steam  cylinder,  driving 
the  piston  downwards.  As  the  piston  and  the  valve  rod  move,  a 
valve  first  closes  the  entry  ports,  thereby  preventing  the  admission 
of  steam  to  the  piston  trunk,  and  later  the  exit  ports  are  closed, 
preventing  the  passage  of  steam  from  the  piston  trunk  into  the 
cylinder.  Later  again,  just  before  the  completion  of  the  stroke,  the 
exit  port  and  another  are  open,  the  steam  then  passing  from  the 
cylinder  into  the  piston  trunk,  and  from  the  piston  trunk  into 
the  chamber  under  the  piston. 

It  has  been  mentioned  that  the  Willans  engine  is  one  of  the  few 
single-acting  engines  at  present  on  the  market.  Steam  is  only 
admitted  to  the  cylinder  while  the  piston  is  moving  downwards,  the 
up  stroke  being  obtained  in  each  engine  by  the  revolution  of  the 
crank  shaft,  this  being  accomplished  by  the  fact  that  when  one 
piston  is  ascending,  the  other  piston  is  descending,  the  engines 
always  being  made  in  pairs,  the  two  crank  shafts  being  180°  apart 
on  the  crank.  In  the  simple  engine  the  steam  passes  from  the 
chamber  under  the  piston,  into  which  it  is  delivered,  directly  to 
the  exhaust.  As  the  piston  commences  its  return  stroke,  the 
guide  piston,  and  the  cushion  or  air  cylinder  immediately  above 
it,  come  into  operation.  When  the  piston  is  at  the  lowest  point 
of  its  stroke,  two  apertures  in  the  air  cylinder  are  open  to  the 
atmosphere,  and  are  filled  with  air  at  atmospheric  pressure.  On 
the  commencement  of  the  up  stroke,  the  air  apertures  are  covered 
by  the  guide  piston,  and  the  air  in  cylinder  immediately  above 
the  guide  piston  is  compressed.  The  object  of  this  arrangement 
is,  to  carry  out  the  system  of  keeping  the  brasses  of  the  cranks,  etc., 
always  in  compression.  It  will  be  evident  that  as  the  steam 
pushes  the  piston  downwards,  the  brasses  between  the  connecting 
rod  and  the  crank  shaft  will  be  forced  downwards,  and  that  there 


234    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

will  be  compression  between  the  connecting  rod  and  the  crank 
shaft.  As  the  piston  rises,  the  same  action  takes  place,  owing  to 
the  compression  of  air  which  is  being  carried  out  in  the  air  cylinder. 
The  work  expended  upon  the  compression  of  the  air  in  the  air  cylinder, 
is  not  lost.  It  is  converted  into  heat,  and  in  the  case  of  a  heat  engine, 
it  is  not  necessary  that  the  heat  should  be  lost.  The  major  portion 
of  the  work  done  in  compressing  the  air  is  returned  to  the  guide 
piston,  and  thence  to  the  piston  trunk,  on  the  down  stroke,  when  the 
air  expands. 

It  was  claimed  by  the  inventor,  and  is  by  the  makers,  that  any 
water  in  the  cylinders  is  carried  directly  into  the  exhaust  with  the 
steam  on  the  up  stroke. 

The  simple  engine  is  sometimes  made  with  three  cranks  and 
three  cylinders,  the  cranks  being  arranged  at  120°  apart  on  the  crank 
shaft,  and  working  in  the  same  manner  as  described  for  the  two 
cylinders. 

With  compound  engines  which  consist  of  simple  engines  with 
the  addition  of  smaller  cylinders  above,  the  action  is  exactly  the  same 
as  in  the  simple  engine.  There  are  two  more  ports  in  the  hollow 
trunk  of  the  piston  rod.  The  valve  rod  is  extended,  and  carries  two 
more  valves,  and  the  steam  enters  the  high-pressure  cylinder  by 
first  passing  into  the  piston  trunk  by  a  valve,  and  out  into  the 
cylinder  behind  the  piston  by  a  port,  the  exhaust  steam  passing  out 
of  the  cylinder  by  way  of  the  piston  trunk  into  the  space  underneath 
the  high-pressure  piston.  There  is  the  slight  difference  between  the 
simple  engifie  and  the  compound  engine,  that  the  exhaust  space  into 
which  the  steam  passes,  after  doing  its  work  in  the  high-pressure 
cylinder,  forms  the  receiver  for  the  steam  that  is  to  be  employed  in 
the  low-pressure  cylinder. 

With  triple -expansion  engines,  which  Messrs.  Willans  &  Eobinson 
have  named  H.H.P.  for  convenience  in  fitting-shop  work,  there  are 
again  two  smaller  cylinders  mounted  above  the  high-pressure 
cylinders  in  the  compound  engine,  the  piston  trunk  extending  up 
through  the  H.H.P.  cylinder,  and  the  valve  rods  also,  the  steam 
passing  into  the  H.H.P.  cylinder,  by  way  of  the  piston  trunk,  and 
passing  out  to  the  exhaust  space  under  the  H.H.P.  piston,  through 
the  piston  trunk,  the  exhaust  space,  as  before,  forming  the  receiver 
for  the  steam  that  is  to  enter  the  H.P.  cylinder. 

It  will  be  noted  that  with  simple  Willaris  engines,  the  steam 
only  remains  in  the  engine  during  one  revolution  of  the  crank  shaft 
as  in  the  ordinary  reciprocating  double-acting  engine,  during  half  of 
the  revolution  the  steam  being  employed  in  driving  the  piston,  and 
during  the  other  half  it  being  engaged  in  escaping  out  of  the  engine. 
In  the  compound  engine  the  steam  remains  within  the  body  of  the 
engine,  during  two  revolutions.  That  is  to  say,  the  steam  entering 


THE  STEAM  ENGINE  235 

the  high-pressure  cylinder  drives  the  high-pressure  piston  to  the  end 
of  the  down  stroke,  and  during  the  up  stroke,  is  engaged  in  passing 
into  the  receiver  or  steam  chest  for  the  low-pressure  cylinder. 
During  the  next  revolution  the  steam  which  worked  the  high- 
pressure  cylinder  during  the  first  revolution,  moves  the  piston  of  the 
low  pressure  cylinder,  during  the  down  stroke,  escaping  to  the 
condenser,  or  the  atmosphere,  during  the  up  stroke.  With  the  triple- 
expansion  engine,  the  steam  remains  within  the  body  of  the  engine 
during  three  revolutions.  During  the  first  revolution  it  is  employed  in 
driving  the  H.H.P.  piston,  and  in  passsing  into  the  H.P.  receiver. 
During  the  second  revolution  it  is  driving  the  H.P.  piston  and 
escaping  to  the  low-pressure  receiver,  and  during  the  third  revolution 
it  drives  the  low-pressure  piston,  and  escapes  to  the  atmosphere  or 
the  condenser.  The  lubricant  for  the  crank  chamber  is  filled  into  it 
through  an  oil  funnel. 

The  Willans  engine  is  controlled  by  a  throttle  governor,  worked 
from  the  crank  shaft.  It  consists  of  the  usual  pair  of  governor 
balls,  revolving  with  the  crank  shaft,  opposed  by  a  spring,  and 
working  by  the  aid  of  a  lever  and  a  vertical  rod,  the  entry  valve  to 
the  steam  chest.  The  steam  enters  by  a  pipe  from  the  steam  supply, 
passing  through  a  valve  leading  from  the  pipe  to  the  steam  chest, 
in  proportion  to  the  amount  the  valve  is  open.  The  quantity  of 
steam  consumed  by  the  engine  is  controlled  entirely  by  the  throttle 
valve,  under  ordinary  circumstances,  but  apparatus  are  added  when 
required  to  enable  expansive  working  to  be  employed  as  well.  The 
cut-off  is  controlled  by  the  position  of  the  gland  rings,  through  which 
the  piston  trunk  passes  at  the  top  of  each  cylinder,  their  position 
being  arranged  by  the  aid  of  distance  piece?. 

There  are  valves  between  the  H.H.P.  distribution  valve  and  the 
H.P.  valve,  and  also  between  the  H.P.  distribution  valve  and  the 
L.P.  distribution  valve. 

The  low-pressure  cylinders  of  all  Willans  engines,  and  the  high- 
pressure  cylinders  of  a  certain  size,  are  fitted  with  internal  relief 
valves,  consisting  of  gun-metal  plugs,  screwed  into  the  top  of  the 
cylinders.  The  plugs  are  pierced  with  holes,  and  are  covered  by  gun- 
metal  discs.  When  the  discs  are  raised,  as  when  the  pressure  in  the 
cylinder  is  above  a  certain  figure,  there  is  free  communication  and 
free  passage  for  the  steam  between  the  cylinder  in  which  the  plug  is 
fixed,  and  the  receiver  or  steam  chest  above  them.  The  discs  are 
kept  down  under  ordinary  working  conditions  by  the  excess  of  the 
pressure  in  the  receiver,  or  the  steam  chest,  above  that  in  the 
cylinder,  a  spring  assisting.  It  is  stated  by  the  makers  that  the 
arrangement  forms  a  perfect  automatic  relief,  in  case  there  is  water 
present  in  the  cylinder. 


236    STEAM   BOILERS,   ENGINES,  AND   TURBINES 
Bumsted  High-Speed  Engine 

The  Bumsted  high-speed  engine,  made  by  Messrs.  Bumsted  and 
Chandler,  was  made  only  single  acting  up  to  a  few  years  ago,  now 
however  two  patterns  are  made,  single  acting  for  sizes  up  to  300  H.P., 
and  double  acting  for  sizes  up  to  600  H.P.  Both  forms  of  engine  are 
made  with  one,  two,  or  three  cranks,  and  for  simple  and  compound 


FIG.  98. — Longitudinal  Section    of    Bumsted  Double-acting  Compound  Enclosed 
Engine,  with  Shaft  Governor. 

engines,  the  double-acting  engine  being  also  made  for  triple  expansion. 
In  both  forms  of  engine  ,the  valves  are  of  the  piston  type. 

In  the  single-acting  engine  the  steam  is  worked  in  a  very  similar 
manner  to  the  Willans  engine.  It  passes  first  into  the  high-pressure 
cylinder,  driving  the  high-pressure  piston  to  the  end  of  its  stroke, 
then  passes  to  the  lower  side  of  the  high-pressure  piston,  this  space 
acting  as  a  receiver ;  and  at  the  next  stroke  it  enters  the  low-pressure 
cylinder  above  the  piston,  drives  the  piston  to  the  end  of  its  stroke, 
and  then  escapes  to  the  exhaust.  The  lubrication  of  the  crank  and 


THE   STEAM   ENGINE 


237 


working  parts  is   effected   on   the  splash  system,  the  crank  shaft 
revolving  in  a  bath  of  oil  and  water. 

In  the  double-acting  engine,  the  bottom  of  the  crank  pit  is  used 
as  an  oil  reservoir,  as  in  the  other  engines  that  have  been  described, 
a  valveless  oil  pump  delivering  the  oil  under  pressure  to  the  bearings 
and  working  parts.  The  governor  is  of  the  throttle  type,  worked 
from  the  crank  shaft.  Fig.  98  is  a  sectional  drawing  of  a  double- 
acting  Bumsted  compound  enclosed  engine,  and  Plate  16A  shows  a 
single  cylinder  Bumsted  enclosed  engine,  Plate  16B  a  compound 
enclosed  engine  made  by  Easton  and  Bessemer. 

The  Peache  Engine 

The  Peache  high-speed  engine,  which  is  made  by  Messrs.  Davey, 
Paxman  &  Co.,  is  also  single  acting,  and  it  has  several  important  dis- 
tinguishing features. 
It  is  nearly  always 
made  with  three 
cranks,  and  with  two 
cylinders,  high-  and 
low  -  pressure,  above 
each  crank.  A  trans- 
verse sectional  drawing 
of  the  engine  is  shown 
in  Fig.  9y.  The  crank 
shaft  works  in  a  bath 
of  oil  and  water,  as  in 
the  other  cases,  and  it 
has  the  special  feature, 
that  in  place  of  being 
fixed  directly  below 
the  centre  line  of  the 
cylinders,  it  is  out  of 
line,  a  little  to  the 
front  of  the  engine,  the 
makers  claiming  that 
this  gives  a  nearly 
straight  connecting  rod 
during  the  downward 
working  stroke,  and 
keeps  a  pressure  on 
the  back  cross  -  head 
slide.  The  valves  also 
are  special  to  the  engine 
are  not  worked  by  eccentrics,  as  is  usually  the  case,  but  by  the 


FIG.   99. — Transverse  Section  of  Peache  High-speed 
Single-acting  Enclosed  Engine. 


They   stand   behind   the   engine,  and 


238    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

rocking  lever  shown  in  Fig.  99,  working  from  a  rod  attached  to 
and  receiving  motion  from  the  connecting  rod.  As  will  be  seen, 
the  valve  rod  is  fixed  vertically,  and  works  vertically,  and  moves 
the  two  valves,  that  controlling  steam  to  the  high-pressure  cylinder, 
and  that  controlling  steam  to  the  low-pressure  cylinder,  by  one 
operation.  In  addition,  there  is  an  air-buffer  cylinder,  that  will  be 
seen  just  above  the  rocking  lever,  which  is  employed  to  overcome 
the  inertia  of  the  valve  at  certain  portions  of  the  stroke,  air  being 
compressed  at  other  portions,  and  giving  up  the  energy  delivered  to 
it  to  overcome  the  inertia  of  the  valve  when  required.  As  will  be 
seen  from  the  drawing  also,  the  high-  and  low-pressure  cylinders  are 
virtually  one,  merely  divided  by  the  piston,  and  they  are  caused  to 
act  as  high-  and  low-pressure  cylinders  by  the  distribution  valves. 
The  steam  enters  by  the  throttle  valve,  which  is  shown  on  the  right 
in  Fig.  99,  into  the  space  surrounding  the  valves,  which  forms  the 
steam  chest.  From  this  it  passes  under  the  edge  of  the  high-pressure 
valve,  to  above  the  high-pressure  piston,  and  after  it  has  forced  the 
high-pressure  piston  to  the  end  of  its  stroke,  it  is  exhausted  over  the 
top  of  the  high-pressure  valve,  down  through  the  main  body  of  the 
valve,  and  over  the  top  of  the  low-pressure  valve,  to  the  under  side  of 
the  low-pressure  piston,  forcing  the  low-pressure  piston  upwards,  the 
high-pressure  piston  going  with  it,  since,  as  will  be  seen,  the  high- 
and  low-pressure  pistons  are  on  one  piston  rod.  The  space  between 
the  high-  and  low-pressure  pistons  is  called  the  controlling  cylinder, 
and  is  arranged  to  be  connected  and  disconnected  by  the  •motion  of 
the  high-pressure  piston,  from  the  space  above  the  high-pressure  piston. 
Hence,  this  space  is  alternately  filled  with  steam  at  the  same  pressure 
as  exists  above  the  high-pressure  piston,  the  steam  is  expanded,  and 
is  compressed  by  the  upward  motion  of  the  low-pressure  piston ;  the 
object  of  the  action  in  the  controlling  cylinder  being  to  balance  the 
upward  inertia  of  the  pistons,  cross  head,  connecting  rod,  etc.,  on  the 
up  stroke,  so  as  to  keep  a  slight  excess  of  pressure  in  a  downward 
direction  throughout  the  up  stroke.  The  work  done  in  compressing 
the  steam  in  the  controlling  cylinder  on  the  up  stroke,  is  given  out 
again  on  the  down  stroke,  by  the  expansion  of  the  steam,  it  acting 
upon  the  low-pressure  piston,  at  the  same  time  as  the  steam  from 
the  steam  chest  is  acting  upon  the  high-pressure  piston.  It  is 
claimed  that  the  arrangement  of  the  valves  behind  the  cylinders 
enables  the  space  occupied  by  the  eccentrics  in  other  engines  to 
be  dispensed  with,  making  the  engine  more  compact.  The'  engine 
has  its  crank  chamber  enclosed,  with  doors  for  access,  the  cylinders 
being  supported  from  the  crank  chamber  by  steel  pillars.  It  will 
also  be  noticed  that  the  connecting  rod  works  in  a  gland  above  the 
crank  chamber,  the  gland  forming  the  end  of  a  dome-shaped  cover, 
which  prevents  oil,  etc.,  from  passing  upward. 


THE   STEAM    ENGINE  239 

The  valve  motion  described  is  made  for  cut-offs  from  0*4  to  0'5, 
from  0*5  to  0'6,  and  from  0'6  to  0*7  in  the  high-pressure  cylinders, 
these  are  fixed  cut-off  gears.  The  engines  are  also  made  for  adjustable 
cut-offs  by  automatic  governors.  The  governor  of  the  Peache  engine 
acts  on  the  throttle  valve,  as  in  the  other  cases. 


Vertical  and  Horizontal  Engines 

Engines  are  arranged  with  their  cylinders  either  in  a  vertical  or 
horizontal  position.  The  older  forms,  the  slow-speed,  and  a  large 
number  of  the  intermediate  speed  engines,  are  arranged  with  their 
cylinders  horizontal,  the  cylinders  and  the  crank  shaft  being  fixed  on 
one  casting,  forming  a  bed  plate.  The  high-speed  engines,  as  men- 
tioned, are  nearly  always  arranged  with  their  cylinders  vertical  and 
inverted,  that  is  to  say,  the  cylinder  stands  above  the  crank  shaft,  the 
piston  rod  projecting  below  the  cylinder,  and  the  crank  shaft  being 
carried  by  a  casting  specially  arranged  for  it,  from  which  pillars  rise 
to  support  the  cylinders  and  the  walls  of  the  enclosing  chamber. 
The  intermediate  speed  engines  are  also  often  arranged  with  their 
cylinders  vertical,  and  inverted  above  the  crank  shaft. 

Where  there  are  two  cylinders,  as  in  the  case  of  compound 
engines,  or  twin-cylinder  engines,  it  is  very  common  to  carry  a  fly- 
wheel on  the  crank  shaft  between  the  engines,  the  cylinders  being 
carried  on  separate  castings,  when  of  the  horizontal  type,  and  in  one 
casting  when  of  the  vertical  type.  As  already  explained,  the  high- 
and  low-pressure  cylinders  of  compound  and  triple-expansion  engines, 
are  sometimes  carried  side  by  side  in  the  vertical  type,  and  some- 
times one  over  the  other.  A  similar  arrangement  rules  with  hori- 
zontal engines,  the  high,  low,  and  intermediate  cylinders  are  sometimes 
carried  in  one  line,  tandem,  on  the  same  bed  plate,  and  sometimes 
side  by  side.  Examples  of  these  are  shown  in  Plates  11  to  14,  and 
Figs.  90  to  92.  Double  compound  engines  of  the  horizontal  type 
are  somewhat  common,  especially  for  pumping  plant,  two  compound 
engines  being  carried  on  each  side  of  a  flywheel,  the  two  cylinders 
of  each  of  the  engines  being  sometimes  one  behind  the  other,  and 
sometimes  side  by  side. 

For  driving  electricity  generators,  and  compressed  air  machinery, 
and,  in  fact,  any  machine  in  which  a  uniform  speed  and  a  uniform 
turning  moment  is  of  importance,  it  is  necessary  to  have  a  flywheel, 
and  this  is  sometimes  carried,  as  explained,  between  the  cylinders, 
in  some  cases  being  made  to  form  part  of  the  electricity  generator, 
while  in  other  cases,  as  in  the  Belliss,  Morcom  and  other  engines, 
the  flywheel  is  carried  between  the  end  of  the  engine  shaft  and  the 
dynamo  shaft. 


240    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

•* 

One  of  the  difficulties  that  has  arisen  in  connection  with  the 
lubrication  of  high-speed  engines,  now  that  the  initial  difficulty  of 
lubricating  continuously  has  been  overcome,  is  the  tendency  of  the 
lubricant  to  work  outwards  from  the  enclosing  chamber  by  every 
path  that  is  open  to  it.  Thus,  where  high-speed  engines  are  con- 
nected to  electricity  generators,  it  is  sometimes  found  that  the 
lubricant  of  the  engine  finds  its  way  over  into  the  armature  or 
revolving  portion  of  the  dynamo,  and  gives  rise  to  some  trouble. 


Lancashire  Mill  Engines 

Lancashire  mill  engines  have  long  had  the  reputation  of  being  the 
most  economical  engines,  so  far  as  the  consumption  of  steam  and 
coal  is  concerned,  that  are  to  be  found  anywhere.  The  Lancashire 
mill  consists  usually  of  a  large  high  building,  on  each  floor  of  which 
are  a  very  large  number  of  spinning  machines,  all  driven  from 
shafting,  and  the  whole  of  the  shafting  on  all  the  floors  is  driven 
from  a  primary  shaft,  which  in  its  turn  is  driven  by  ropes  from  a 
heavy  flywheel  pulley,  worked  by  a  pair  of  engines,  between  which 
the  pulley  is  fixed.  The  engines  are  sometimes  compound,  and  some- 
times triple  expansion,  there  being  the  usual  controversy  as  to  which 
is  the  better  arrangement. 

The  rope  drive,  however,  is  gradually  being  displaced  in  the  mills 
that  are  now  being  put  down,  and  in  some  of  the  older  mills,  by  the 
electric  motor  drive,  the  main  engines  being  employed  to  drive  a 
generator  in  the  engine-house,  and  a  motor  being  fixed  either  on  each 
floor,  or  more  than  one  on  each  floor,  taking  current  from  the  main 
generator,  and  driving  the  shafting,  which  in  its  turn  drives  the 
spinning  machinery.  As  an  illustration  of  the  horizontal  triple - 
expansion  condensing  engines  that  have  done  such  good  work,  the 
following  made  by  Messrs.  Daniel  Adamson,  of  Dukinfield,  will 
probably  be  interesting.  The  engine  is  shown  in  Plate  12.  There 
are  two  cylinders  on  each  side  of  the  driving  pulley,  the  low- 
pressure  cylinder  being  divided  into  two,  as  explained  on  a  previous 
page.  On  one  side  is  the  high-pressure  cylinder,  and  one  low- 
pressure  cylinder,  and  on  the  other  side  is  the  intermediate  and 
the  other  low-pressure  cylinder.  The  high- pressure  cylinder  is  14 
inches  diameter,  the  intermediate  24  inches,  and  the  two  low- 
pressure  cylinders  each  26  inches,  the  common  stroke  being  4  feet, 
and  the  engine  running  at  70  revolutions  per  minute,  and  deliver- 
ing 600  I.H.P.  with  an  initial  steam  pressure  of  160  Ibs.  per  square 
inch.  It  will  be  noticed  incidentally  that  the  piston  speed  is  560 
feet  per  minute,  which  is  practically  the  same  as  that  of  the  so- 
called  high-speed  engines.  The  pistons  of  the  high-pressure  and 


PLATE  15A. — Triple  Expansion  Marine  Engine,  made  by  the  Central  Engineering 

Works,  Hartlepool. 


PLATE  15B.— Single  Cylinder  Corliss  Valve  Engine,  with.  Shaft  Governor,  made  by 

the  Atlas  Co.  [To  face  p.  240. 


THE  STEAM  ENGINE 


241 


low-pressure  are  attached  to  one  piston  rod,  and  deliver  by  one  con- 
necting rod  to  one  crank  shaft  on  one  side  of  the  driving  pulley,  the 
pistons  of  the  intermediate  and  low-pressure  cylinders  being  also  on 
one  piston  rod,  and  delivering  by  one  connecting  rod  to  a  crank  shaft 
on  the  other  side  of  the  driving  pulley.  Each  pair  of  engines  has 
its  own  governor,  its  own  condenser,  air  pump,  and  boiler-feed  pump. 
The  high  and  intermediate  cylinders,  and  the  working  parts  of  the 
engine,  are  fixed  on  trunk  girders,  and  the  two  engines  are  provided 
with  distance  pieces,  the  low-pressure  cylinders  being  fixed  on 
separate  cast-iron  bed-plates,  secured  to  the  foundations,  provision 
being  made  for  the  feet  of  the  cylinders  to  slide  freely,  so  as  to 


FIG.  100. — Section  of  Cylinder  of  Lancashire  Mill  Engine,  with  "  Wheelock"  Valves. 
The  Valve  is  seen  in  section  below  the  Cylinder,  on  the  left.  It  controls  the 
entry  and  exit  of  the  Steam,  and  is  claimed  to  combine  the  advantages  of  the 
Slide  and  Corliss  Valves.  The  Expansion  Gear  is  shown  on  the  right. 

accommodate  themselves  to  the  expansions  and  contractions  of  the 
engines.  The  condensers  are  fixed  underneath  the  main  frames  of 
the  engines,  the  air  pumps  and  boiler-feed  pumps  being  also  fixed 
there.  The  air  pumps  are  driven  direct  from  the  main  engine  cross 
head  by  steel  plate  levers  and  links  provided  for  the  purpose,  and 
the  boiler  feed  pumps  are  driven  from  the  air-pump  levers. 

The  driving  pulley  is  18  feet  in  diameter,  and  is  grooved  to 
take  twenty  If  inch  ropes,  the  speed  of  the  ropes  being  3960  feet 
per  minute,  and  the  drum  being  built  up  in  segments. 

The  high  and  intermediate  cylinders  are  each  fitted  with  auto- 
matic expansion  gear  controlled  by  their  own  governors,  the  expan- 
sion gear  being  of  the  Wheelock  type,  the  general  arrangement  of 

R 


242    STEAM  BOILERS,  ENGINES,  AND   TURBINES 

which  is  shown  in  Fig.  100.  The  valves  also  are  of  the  type 
B  Wheelock  pattern,  and  the  gridiron  arrangement  is  clearly  shown 
in  the  sectional  drawing.  The  automatic  expansion  gear  is  claimed 
to  give  control  of  the  expansion  from  zero  up  to  75  per  cent,  of  the 
piston's  stroke  while  retaining  complete  control  of  the  periods  of 
release  and  compression.  It  is  claimed  that  the  arrangement  of  a 
toggle  joint  between  the  valve  grids  and  spindles  gives  almost 
instantaneous  opening  and  closing,  with  great  ease  of  action  under 
extreme  pressures.  Instantaneous  opening  and  closing,  it  will  easily 
be  understood,  is  of  great  importance,  inasmuch  as  it  gives  the 
engineer  practically  complete  control  of  his  engine.  Plate  17A  shows 
a  horizontal  cross  compound  with  engine,  made  by  Messrs.  Galloway. 

Reciprocating  Valves  for  Engines 

It  has  been  explained  that  the  piston  is  caused  to  move  to  and 
fro  in  the  cylinder  of  the  engine  by  the  admission  of  steam  alternately 
on  each  side  of  it,  and  one  of  the  problems  which  engine  builders 
have  had  to  solve  has  been  the  construction  of  a  valve  that  would 
accomplish  this.  There  are  the  following  forms : — 

The  slide  vahe.  The  Corliss  valve. 

The  Cornish  valve.  The  trip,  or  drop,  valve. 

And  special  forms  of  valves,  such  as  the  central  valve  enjoyed  in  the 
Willans  engine  and  others. 

The  slide  valve  was  the  earliest  form.  The  problem,  it  will  be 
understood,  is  to  bring  the  supply  of  steam,  which  is  usually  con- 
tained in  a  part  of  the  engine  called  the  steam  chest,  into  connection 
with  the  end  of  the  cylinder,  to  which  steam  is  to  be  admitted  at  the 
moment,  and  to  bring  each  end  of  the  cylinder  into  connection  with 
the  exhaust  later.  It  should,  perhaps,  be  mentioned  lirst  that  the 
cylinder  of  the  steam  engine  nearly  always  forms  part  of  a  casting  in 
which  the  entry  valves,  as  the  valves  controlling  the  admission  of 
steam  are  called  generically,  are  arranged  to  work,  and  also  with  a 
space  or  chamber,  called  the  "  steam  chest,"  into  which  the  steam 
is  admitted  from  the  steam  pipe,  and  from  which  it  passes  through 
ports  at  each  end  of  the  cylinder  into  the  cylinder  at  the  proper 
moment.  What  is  called  a  "  stop  valve,"  which  controls  the  admis- 
sion of  steam  from  the  steam  pipe  to  the  steam  chest,  is  fixed  between 
the  steam  pipe  and  the  casting  forming  the  cylinder.  The  governor, 
which  also  controls  the  admission  of  steam  to  the  steam  chest,  is 
frequently  carried  by  the  cylinder  casting.  The  stop  valve  is  an 
arrangement  consisting  of  fixed  portions  and  a  moving  portion, 
which  is  moved  usually  by  turning  a  hand  wheel.  As  the  wheel 
is  turned  in  one  direction,  a  small  opening  is  made  between  the 


THE  STEAM  ENGINE  243 

parts  of  the  valve,  through  which  the  steam  enters  and  passes  to 
the  steam  chest.  As  the  valve  wheel  is  screwed  back  more  and 
more,  the  space  through  which  the  steam  passes  is  increased  until 
the  valve  is  wide  open  and  the  sectional  area  of  the  space  avail- 
able for  the  steam  is  equal  to  that  of  the  steam  pipe  supplying 
the  engine.  When  there  is  a  governor  also  carried  by  this  part 
of  the  engine,  it  is  of  the  throttle  type,  that  is  explained  further 
on,  and  it  performs  exactly  the  same  operation  automatically,  in 
obedience  to  changes  of  rate  of  motion  received  from  the  crank  shaft, 
as  the  stop  valve  does  when  moved  by  hand.  It  will  be  understood 
that  the  supply  of  steam  to  the  engine  can  be  controlled  by  the  stop 
valve,  and  that  when  the  engine  is  only  required  to  do  small  work 
the  stop  valve  is  only  open  a  small  distance,  and  when  more  work  is 
put  on  it,  the  stop  valve  is  opened  wider,  and  so  on.  With  properly 
governed  engines,  it  is  usual,  in  a  great  many  forms  of  work,  to  throw 
the  stop  valve  wide  open  when  once  the  engine  has  taken  its  load, 
and  leave  the  governor,  as  will  be  explained,  to  control  the  supply  of 
steam.  On  the  other  hand,  in  some  cases  the  control  afforded  by  the 
stop  valve  is  of  great  service.  Such  a  case  is  that  of  alternate  cur- 
rent electricity  generators,  driven  by  steam  engines,  at  the  moment 
when  a  particular  generator  is  being  brought  to  synchronism  with 
the  others  already  at  work.  One  of  the  factors  in  the  problem  of 
synchronism  is  the  speed  of  the  generator,  and  this  is  controlled 
most  easily  by  the  stop  valve.  When  an  alternating  current  gene- 
rator is  to  be  connected  to  the  bus  bars,  the  engine  driver  gradually 
brings  it  up  to  about  its  proper  speed  by  gradually  opening  the  stop 
valve,  and  he  and  the  switch-board  attendant  bring  it  to  synchronism, 
by  alternately  moving  the  stop  valve  and  changing  the  exciting 
current  of  its  field  magnets.  Similarly,  when  any  engine  is  being 
started  from  rest,  it  is  brought  gradually  up  to  speed  by  gradually 
opening  the  stop  valve.  One  reason  for  this  is,  the  engine  being 
cold,  condensation  will  take  place  very  rapidly,  and  give  some 
trouble  unless  the  cylinders  are  warmed  up.  They  are  warmed  by 
the  admission  of  a  small  quantity  of  steam  through  the  stop  valve, 
the  drain  cocks,  which  are  fitted  to  all  cylinders,  being  opened  to 
allow  any  water  that  is  formed  by  condensation,  or  that  may  have 
been  present,  to  be  driven  out  by  the  steam.  The  stop  valve,  as 
explained  on  page  256,  is  itself  warmed  before  being  put  in  operation, 
by  steam  passing  through  a  small  bypass  arranged  for  the  purpose. 


The  Slide  Valve 

The  slide  valve,  as  its  name  implies,  slides  upon  a  planed  surface 
provided  for  it,  usually  on  the  side  of  the  cylinder.     Sections  and 


244    STEAM  BOILERS,  ENGINES,  AND   TURBINES 

forms  of  slide  valves  are  shown  in  Figs.  101  and  102.    In  its  simplest 
form,  it  consists  of  a  metal  box  of  rectangular  section  without  a  cover, 


FIG.  101. — Section  of  one  form  of  Slide  Valve. 

the  hollow  portion  being  placed  against  the  surface  of  the  cylinder 
upon  which  it  slides.     It  is  sometimes  fitted  with  projections,  laps  as 


FIG.  102.-    Section  of  another  form  of  Slide  Valve. 

they  are  called,  on  each  side  of  the  walls  of  the  box.     The  box  moves 
to  and  fro  inside  a  slide  case  forming  the  steam  chest,  to  which  steam 


THE   STEAM   ENGINE  245 

is  admitted,  as  shown  in  the  figures,  and  the  steam  passes  into  the 
cylinder  through  either  of  the  ports  leading  to  either  side  of  the 
piston,  when  the  slide  valve  uncovers  that  port  and  leaves  it  open 
to  the  steam  present  in  the  steam  chest.  The  modus  operandi  is  as 
follows:  With  the  valve  in  its  middle  position,  both  of  the  ports 
leading  into  the  cylinder  are  closed  by  the  slide  valve  standing  over 
them.  As  the  valve  moves  to  the  right  the  cylinder  entry  port  on 
the  left  is  gradually  uncovered,  the  steam  then  passing  from  the 
slide  jacket  through  that  entry  port  behind  the  piston,  which  then, 
as  explained,  is  moved  to  the  right  in  the  cylinder.  At  a  certain 
period  of  the  stroke,  arranged,  as  will  be  explained,  by  the  aid 
of  the  eccentric  controlling  the  travel  of  the  slide  valve,  the  valve 
commences  to  return,  and  gradually  closes  the  entry  port  to  the 
cylinder  on  the  left.  After  the  valve  has  travelled  a  certain  distance, 
the  entry  port  on  the  left  is  not  only  closed  to  the  space  behind  the 
valve  but  is  open  to  the  hollow  space  in  the  middle  of  the  valve,  and 
this  is  open  to  the  exhaust  by  the  passage  shown.  At  the  same 
moment,  though  sometimes  a  little  later,  and  again  sometimes  a  little 
earlier,  according  to  the  conditions  of  working,  the  wall  of  the  slide 
valve  on  the  right  commences  to  uncover  the  entry  port  into  the 
steam  cylinder  on  the  right,  the  steam  then  passing  into  the  cylinder 
behind  the  piston,  which  is  now  at  the  right  hand  of  the  cylinder, 
the  piston  now  commencing  to  travel  from  right  to  left.  At  a  certain 
portion  of  the  stroke,  the  slide  valve  again  commences  to  return, 
gradually  closing  the  entry  port  on  the  right,  and  then  opening  the 
entry  port  to  the  hollow  space  in  the  middle  of  the  slide  and  thence 
to  the  exhaust,  the  entry  port  on  the  left  then  commencing  to  be 
uncovered,  and  so  on. 

For  large  engines,  however,  the  simple  slide  valve  is  not  found 
satisfactory,  because  it  would  be  obliged  to  be  made  too  large  and  to 
have  a  very  long  travel.  To  meet  this,  double-ported  slide  valves 
are  employed,  in  which  the  entry  ports  to  the  engine  cylinder  are 
larger  than  with  the  simple  slide  valve,  and  there  are  two  spaces  lead- 
ing into  them  which  are  swept  over  by  two  portions  of  the  surface  of 
the  slide  valve.  The  slide  valve,  again,  is  divided  up,  the  central 
portion  and  the  portion  surrounding  the  two  additions  on  the  right 
and  left  making  connection  with  the  exhaust,  while  the  back  of  the 
slide,  where  the  steam  chest  is,  is  in  communication  with  the  additional 
portions  to  right  and  left.  Taking  the  valve  in  its  central  position, 
with  all  ports  closed,  and  suppose  it  to  move  to  the  right,  the 
left-hand  portion  of  the  left-hand  entry  port  will  be  uncovered 
by  the  main  body  of  the  slide,  while  the  right-hand  portion  of  the 
same  entry  port  will  be  placed  in  communication  with  the  hollow 
part  of  the  left-hand  addition  to  the  slide,  which  is  also  in  communi- 
cation with  the  steam  chest,  the  steam  then  passing  through  both 


246    STEAM  ENGINES,  BOILERS,   AND   TURBINES 

portions  of  the  entry  port  into  the  steam  cylinder  to  the  left  and 
behind  the  piston,  forcing  it  over  to  the  right.  At  a  certain  portion 
of  the  stroke,  the  slide  valve  commences  to  return  and  to  gradually 
close  the  two  portions  of  the  entry  port,  and,  later,  to  open  both 
portions,  one  to  the  hollow  space  in  the  centre  of  the  slide,  and 
the  other  to  the  space  on  the  left  leading  to  the  same  hollow  space, 
and  both  leading  to  the  exhaust.  The  action  of  the  double-ported 
slide  is  exactly  the  same  in  other  respects  as  that  of  the  single- 
ported.  As  the  slide  moves  again  to  the  left,  the  steam  is  admitted 
to  the  right-hand  entry  port  behind  the  piston  which  is  now  at 
the  right-hand  end  of  the  cylinder,  and  commences  to  move  it  to 
the  left,  and  again,  at  a  certain  portion  of  the  stroke,  the  slide 
commences  to  close  both  portions  of  the  right-hand  entry  port,  and 
a  little  later  to  open  both  to  the  hollow  portion  of  the  valve,  and 
thence  to  the  exhaust. 


Giving  Motion  to  the  Slide  Valve 

Motion  is  given  to  the  slide  valve  by  means  of  a  rod  worked  from 
the  crank  shaft,  the  to  and  fro  motion  being  obtained  by  what  are 
termed  eccentrics.  It  is  well  understood  that  when  a  disc  is  pivotted 
at  its  centre,  any  rod  attached  to  its  periphery  will  have  a  to  and  fro 
motion  exactly  the  same  in  each  direction,  just  as  the  crank  shaft  has ; 
in  fact,  in  some  cases,  a  disc  is  employed  in  place  of  a  crank  shaft. 
A  disc,  however,  has  the  advantage,  by  proper  arrangement,  that  the 
amount  of  the  to  and  fro  motion  can  be  regulated.  Thus,  if  a  rod  is 
connected  to  the  periphery  of  a  disc  12  inches  in  diameter,  the  total 
travel  of  the  rod  will  be  12  inches,  while  if  it  is  connected  to  a  point 
only  1  inch  from  the  centre,  its  travel  will  be  only  2  inches,  and  so 
on  in  proportion.  The  rod  which  gives  motion  to  the  slide  is  con- 
nected to  a  certain  point  on  a  disc,  the  disc  working  on  the  crank 
shaft,  the  travel  of  the  crank  shaft,  or  the  throw  of  the  eccentric, 
depending  upon  the  distance  of  the  attachment  of  the  rod  to  the  disc 
from  the  centre  of  the  crank  shaft.  In  expansion  governors,  as  will 
be  explained,  it  is  arranged  to  increase  or  decrease  the  throw  of  the 
eccentric  by  the  increase  or  decrease  of  speed  of  the  engine. 

The  object  of  this  is  to  increase  or  decrease  the  time  during  which 
the  entry  port  of  the  cylinder  is  open  to  the  steam  chest.  It  will  be 
understood  that  as  the  slide  valve  moves  across  the  cylinder,  it 
gradually  exposes  a  portion  of  the  cylinder  entry  port  to  the  steam 
chest.  As  it  moves  onward  in  the  same  direction,  the  space  opened 
gradually  increases  until,  if  it  is  allowed  to  do  so,  the  entry  port 
is  fully  exposed  to  the  steam  chest.  This  is  the  case  explained  on  a 
previous  page,  where  the  engine  is  not  worked  expansively,  and 


THE   STEAM   ENGINE  247 

where  the  steam  merely  pushes  the  piston  to  the  end  of  its  stroke. 
It  was  explained,  however,  that  for  economy  the  steam  is  only  allowed 
to  enter  for  a  certain  portion  of  the  stroke,  usually  from  half  of  the 
stroke  downwards  to  as  low  as  one-tenth,  and  this  is  accomplished  in 
the  case  of  the  slide  valve  by  only  allowing  it  to  travel  J,  J,  or  y1^, 
as  the  case  may  be,  of  the  stroke  before  it  commences  to  return,  the 
amount  of  travel  being  arranged  so  that  the  port  only  remains  open 
altogether  for  the  proportion  of  the  stroke  decided  upon.  This 
variable  length  of  travel  of  the  slide  is  accomplished  by  varying  the 
position  of  the  pin  upon  which  the  eccentric  rod  works  in  the  disc 
which  carries  it  round  the  crank  shaft.  For  reversing  the  engine 
two  eccentrics  are  employed,  one  taking  charge  of  the  slide  when  the 
engine  is  running  in  its  normal  direction,  and  the  other  taking  charge 
of  it  when  the  engine  is  running  in  the  reverse  direction.  It  will 
be  understood  that  the  direction  of  motion  of  the  engine  can  be 
reversed  by  admitting  steam  to  the  opposite  side  of  the  piston  to 
that  at  which  it  would  be  admitted  to  move  it  in  the  direction  in 
which  it  would  travel  if  running  normally,  and  this  is  accomplished 
by  what  is  called  link  motion,  and  which  is  arranged  to  change  the 
eccentric  controlling  the  motion  of  the  slide  rod  from  that  which  moves 
the  slide,  so  that  steam  enters  the  cylinder  normally,  to  that  which 
moves  the  slide,  so  that  it  enters  on  the  opposite  side  of  the  piston. 
The  link  motion  consists  of  a  link  or  arc  of  a  circle,  to  which  the  rod 
moving  the  slide  is  attached  in  such  a  manner  that  the  pin  connecting 
it  to  the  link  can  move  along  from  one  end  of  the  arc  to  the  other. 
To  the  ends  of  the  arc  are  attached  the  two  rods  connected  to  the  two 
eccentrics,  one  at  each  end  of  the  arc.  When  the  slide  rod  is  midway 
between  the  two  eccentric  rods  there  is  no  motion  of  the  slide  rod  at 
all,  and  when  it  is  pulled  to  one  end  of  the  arc  it  forms  a  continuous 
rod  with  one  of  the  eccentric  rods,  that  eccentric  then  controlling  the 
slide  motion,  the  other  one  being  out  of  gear.  To  reverse  the  direction 
of  motion,  the  slide  valve  is  moved  through  the  arc  to  the  other  end, 
where  it  forms  a  line  with  the  other  eccentric  rod  which  then  controls 
the  slide  motion. 


Objections  to  the  Slide  Valve 

There  are  several  objections  to  the  slide  valve,  which  have 
gradually  caused  it  to  fall  into  disuse.  One  is,  that  considerable 
leakage  of  steam  often  takes  place,  owing  to  the  valve  surfaces 
becoming  worn,  and  providing  a  space  through  which  the  steam 
escapes.  If  the  slide  valve  is  to  accurately  control  the  admission 
of  steam  to  the  engine,  there  must  be  no  possibility  of  the  steam 
escaping,  say,  along  the  face  of  the  slide  to  the  exhaust  valve ;  but 


248    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

this  is  what  takes  place,  unfortunately,  when  the  slide  is  worn,  the 
steam  so  passing  being  lost  for  useful  purposes,  and  increasing  the 
amount  of  coal  consumed  in  the  boiler  furnace  uselessly.  Further, 
the  steam  which  passes  through  the  cracks  so  formed  tends  to  increase 
them,  and  thereby  to  increase  the  leak.  On  the  other  hand,  there 
are  complaints  that  very  great  friction  is  often  set  up  between  the 
face  of  the  slide  valve  and  the  surface  of  the  cylinder  upon  which  it 
works,  owing  to  the  pressure  of  the  steam  behind  the  slide,  this 
friction  leading  to  wear  and  to  leakage.  This  has  led  to  various 
forms  of  what  are  known  as  balanced-slide  valves,  in  which  smaller 
slide  valves  are  placed  behind  the  main  valve,  and  are  so  arranged 
as  to  relieve  the  pressure  of  the  steam  upon  the  back  of  the  valve, 
and  facilitate  its  comparatively  easy  motion. 


Lap  and   Lead  of  Slide  Valve 

The  surface  of  the  slide  valve  that  is  in  contact  with  the 
surface  of  the  cylinder  over  which  it  moves,  extends  beyond  the 
actual  cover  forming  the  port  through  which  the  steam  passes  to 
the  cylinder  and  to  the  exhaust,  and  these  extensions  at  either  end,  it 
will  be  easily  understood,  tend  to  change  the  time  during  which  the 
entry  port  is  open  to  the  steam  chest ;  and,  again,  during  which  the 
other  entry  port  is  open  to  the  exhaust.  These  extensions  are  known 
as  lap  and  lead,  and  they  can  be  arranged  to  effect,  permanently,  what 
is  effected  by  the  variation  in  the  throw  of  the  eccentric. 


The  Piston  Slide  Valve 

In  the  piston  slide  valve  the  admission  of  steam  to  the  cylinder, 
and  the  egress  of  steam  from  the  cylinder  to  the  exhaust  pipe,  are 
controlled  by  valves  having  the  form  of  short  solid  cylinders,  similar 
in  form  to  engine  pistons,  and  known  as  piston  valves.  They  perform 
exactly  the  same  office  as  the  slide  valve  does,  and  in  very  much 
the  same  way.  There  is  the  same  steam  chest,  or  valve  case,  the 
same  entry  ports  leading  to  the  steam  cylinder,  and  the  surfaces  of 
the  piston  valve  perform  the  same  office  of  closing  the  entry  ports 
leading  to  the  steam  cylinder,  as  the  walls  of  the  slide  valve  do. 
The  body  of  the  piston  valve  is  cut  away  in  the  centre,  this  forming 
a  hollow,  corresponding  to  the  hollow  space  formed  by  the  ordinary 
slide  valve.  The  action  of  the  valve  is  exactly  the  same.  Assum- 
ing the  valve  to  be  in  its  central  position,  when  both  entry  ports 
are  closed  by  the  larger  portion  of  the  piston  valve  at  each  end, 
and  suppose  the  valve  to  move  upwards,  the  entry  port  leading 


PLATE  15c. — Vertical  Compound  Enclosed  Engine,  with  Steam  Separator,  and  driving 
a  Dynamo,  made  by  Eastan  &  Bessemer. 


PLATE  16A. — Bumsted  Single  Cylinder  Vertical  Encased  Engine,  driving  a  Dynamo. 

[To  face  p.  248. 


THE   STEAM   ENGINE  249 

to  the  lower  part  of  the  steam  cylinder  will  gradually  be  un- 
covered, steam  entering  the  steam  cylinder  from  the  steam  chest, 
through  it,  and  driving  the  piston  upwards.  At  the  same  time  a 
portion  of  the  hollow  space  in  the  centre  of  the  piston  valve  will 
come  opposite  the  upper  entry  port  of  the  steam  cylinder,  and  the 
steam  will  flow  out  from  the  upper  part  of  the  cylinder  into  the 
hollow  space,  and  thence  to  the  exhaust.  At  a  certain  portion  of 
the  stroke,  as  with  the  slide  valve,  the  piston  valve  will  commence 
to  move  downwards,  gradually  closing  the  lower  entry  port  of  the 
steam  cylinder,  and  gradually  closing  the  opening  between  the  upper 
entry  port  and  the  exhaust.  As  the  valve  continues  to  move  down- 
wards, the  upper  entry  port  will  be  gradually  opened  in  the  steam 
chest,  and  the  lower  entry  port  to  the  hollow  space  in  the  middle  of 
the  piston  valve,  and  to  the  exhaust,  and  so  on. 

The  piston  valve  receives  motion  from  the  crank  shaft  by  means 
of  rods  worked  by  eccentrics,  just  as  the  slide  valve  does. 

It  will  be  seen  that  with  this  form  of  valve  there  is  not  so  much 
danger  of  leakage  of  steam  past  the  valve  into  the  exhaust,  and  it  is 
more  commonly  employed  for  high  pressures,  while  there  is  also  not 
the  same  pressure  forcing  it  against  the  surface  of  the  cylinder  as  in 
the  ordinary  slide  valve.  Several  forms  of  high-speed  engines  use 
this  valve. 

Drop  Valves 

The  drop  valve,  one  form  of  which  is  shown  in  section  in  Fig.  103, 
has  been  adopted  by  Messrs.  Eobey,  Messrs.  Marshall,  and  others, 
for  some  of  their  engines.  The  valve  which  is  shown  at  A  in  the 
drawing  is  in  equilibrium,  that  is  to  say,  the  pressure  of  the  steam 
is  the  same  on  each  side  of  it,  and  it  is  arranged  for  the  steam  to 
pass  into  the  cylinder  when  the  valve  is  lifted.  Attached  to  the 
engine  is  an  arm  shown  with  an  eccentric  on  it,  taking  motion  by 
bevelled  gear  from  the  crank  shaft,  and  working  the  eccentric  rod  K, 
which  gears  with  a  rod  marked  B  in  the  drawing,  pivotted  as  shown, 
the  other  end  of  which  engages  with  the  vertical  rod  supporting  the 
valve.  As  the  eccentric  moves  round,  the  eccentric  rod  K  describes 
an  arc,  in  the  course  of  which  it  depresses  the  end  of  the  lever  B, 
raising  the  rod  attached  to  the  valve  rod,  and  opening  it,  the  steam 
then  entering  the  cylinder.  As  the  eccentric  rod  moves  on,  as  the 
stroke  proceeds,  the  tripping  gear  attached  to  the  end  of  the  rod  is 
disengaged  from  the  lever  B,  and  the  spring  above  the  valve  A 
immediately  closes  it.  It  is  arranged  that  the  eccentric  rod  shall 
engage  with  the  lever  B,  just  before  the  commencement  of  the  stroke, 
and  the  disengagement  is  controlled  either  by  the  governor,  or  by 
screws  provided  for  the  purpose.  Fig.  103  also  shows  the  same  valve 


250    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

arranged  for  the  exhaust,  a  second  eccentric  rod  being  carried  as 
shown  below  the  other  one,  and  opening  the  exhaust  valve  in  the 
lower  part  of  the  cylinder,  through  which  the  steam  passes  to 


FIG.  103. — Transverse  Section  of  Cylin- 
der with  Drop  Valve,  with  Trip  Gear, 
as  made  by  Messrs.  Marshall. 


FIG.  104. — Longitudinal  of  Cylinder, 
with  Drop  Valves  and  Trip  Gear  for 
Steam  Entry  and  Exhaust. 


the  exhaust  pipe  and  to  the  condenser,  etc.  It  will  be  seen  by  the 
drawing  in  Fig.  104,  showing  a  complete  cylinder,  that  there  are  drop 
valves  for  each  side  of  the  piston  for  entry,  and  also  for  exhaust. 
Plate  1?B  is  a  view  of  a  cylinder  fitted  with  trip  gear  and  the  governor. 


The  Piston   Drop  Valves 

The  piston  drop  valve,  made  by  Messrs.  CoL%  Marchent,  and  Morley 
of  Bradford,  is  worked  in  a  similar  manner  to  the  drop  valves  previously 
described,  but  the  body  of  the  valve  is  a  solid  cylinder,  and  not  of 
the  usual  mushroom  form  employed. 


Cornish   Valves 

The  Cornish  valve  is  really  a  drop  valve.  It  is  very  much  used 
in  winding  engines  for  mines,  and  was  also  used  in  the  old  Cornish 
pumping  engines.  It  is  an  equilibrium  valve,  like  the  drop  valves 
described.  The  valve  is  usually  fixed  in  its  own  valve  box,  forming 


THE   STEAM   ENGINE 


251 


part  of  the  engine  casting,  and  is  lifted  by  a  lever,  worked  by  the 
eccentric  rod  from  the  crank  shaft,  it  being  lifted  off  its  seat  at  the 
proper  moment,  and  dropped  back  and  forced  into  its  seat  at  the  point 
of  cut  off  by  weights  fixed  on  the  valve  rod  above. 


The  Corliss  Valve 

The  Corliss  valve,  which  is  an  American  design,  is  in  the  form 
of  a  hollow  cylinder,  but  in  place  of  rising  and  falling  in  a  port 


FIG.I 


FIG.  105. — Arrangement  of  Corliss  Valves,  with  Wrist  Plate,  as  made  by  the  Fulton 
Co.  of  America.  S  S  are  the  Chambers  for  Steam  Entry ;  E  E  those  for  Exhaust ; 
B  is  the  Wrist  Plate ;  K  K  and  L  L  the  Levers  transmitting  Motion  from  it  to 
the  Levers  D  D,  N  N  which  move  the  Valves;  A  is  the  eccentric  Hod  moving 
the  Wrist  Plate;  H  H  are  Kods  connected  with  the  Governors  actuating  the 
cut  off ;  P  P  are  Dash  Pots. 

provided  for  it,  it  revolves  within  the  port.  Fig.  105  shows  the 
arrangement  of  the  valve.  The  valve  is  usually  fitted  to  horizontal 
engines,  and  that  there  are  four  such  valves  placed  around  the 
cylinder,  and  worked  by  the  system  of  rods  shown,  from  the 
crank  shaft.  The  cylinders  forming  the  valves  have  portions  cut 
away,  and  the  casting  forming  the  side  of  the  cylinder,  in  which 
the  valves  work,  has  ports  leading  from  the  steam  chest  to  the 
steam  cylinder,  and  when  a  space  in  the  valve  is  opposite  to  two 
spaces  in  the  cylindrical  aperture  in  which  it  works,  steam  passes 


252     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

through  it,  from  the  steam  chest  to  the  cylinder.  Fig.  106  is  a 
sectional  drawing  of  a  single  cylinder  engine  with  Corliss  valves,  in 
which  the  forms  of  the  valves  are  clearly  shown.  Again,  when 
portions  cut  away  in  the  valve  are  opposite  the  entry  port  to  the 
cylinder,  and  a  port  leading  to  the  exhaust,  the  steam  passes  through 
the  valve  from  the  cylinder  to  the  exhaust  pipe.  The  valve  is 
rotated  as  shown  by  rods  from  the  crank  shaft,  and  is  usually  brought 
back  by  springs.  It  will  be  understood  that  the  time  during  which 
steam  is  admitted  to  the  cylinder  on  either  side  of  the  piston,  can  be 
controlled  by  the  time  during  which  the  cut  away  portions  in  the 
valves  are  opposite  the  passages  leading  to  the  steam  cylinder,  and 
this  is  controlled  by  devices  to  be  explained.  The  four  valves  are 
worked  by  four  rods  from  a  disc  known  as  a  wrist  plate,  which  is 


FIG.  106. — Section  of  Single  Cylinder  Engine,  with  Corliss  Valves,  made  by  the 
Atlas  Co.    The  form  of  the  Entry  and  Exhaust  Valves  are  clearly  shown. 

pivoted,  as  shown  in  Fig.  105,  on  the  side  of  the  engine  cylinder,  to 
which  the  four  rods  are  attached,  and  a  rod  leading  to  an  accentric  on 
the  crank  shaft.  The  eccentric  rod  moves  the  wrist  plate  to  and 
fro  upon  its  central  pivot,  and  the  plate  moves  the  rods  to  and  fro  in 
their  order,  the  rods  moving  the  valves.  Assuming  the  piston  to  be 
at  the  left  of  the  cylinder,  the  entry  valve  at  the  top  left-hand  corner 
is  opened  by  its  rod,  remaining  open  for  a  certain  time,  and  is  then 
closed,  and  at  the  end  of  the  stroke,  or  slightly  before,  or  again  a 
little  after,  as  may  be  arranged,  the  valve  on  the  lower  left-hand 
corner  is  opened  by  its  rod,  the  steam  passing  into  the  cylinder  when 
the  upper  valve  is  opened,  during  the  time  it  remains  open,  and 
passing  out  to  the  exhaust  when  the  lower  valve  is  opened.  When 
the  piston  arrives  at  the  right-hand  end  of  the  cylinder,  or  a  little 
before,  as  may  be  arranged,  the  entry  valve  at  the  right-hand  top 


THE   STEAM  ENGINE 


253 


corner  is  opened,  steam  passing  into  the  cylinder,  the  exhaust  valve 
at  the  right-hand  lower  corner  being  opened  at  the  end  of  the  stroke, 
and  so  on,  these  motions  corresponding  to  the  motions  of  the  slide 
valve.  The  working  of  the  valves  themselves, -by  the  rods  from  the 
wrist  plate,  is  not  quite  so  simple.  The  steam  entry  valves  are  also 
under  the  control  of  the  governor,  as  shown  in  Fig.  105,  being  allowed 
to  remain  open  a  longer  or  shorter  time  as  with  the  slide.  The  Corliss 
valve  is  liked  because  it  enables  economical  steam  working  to  be 


FIG.  107. — Double  Cylinder  Corliss  Engine,  made  by  the  Fishkill  Co.,  of  America. 

obtained,  there  being  little  friction,  compared  with  the  slide  valve, 
and  smaller  chance  of  leakage,  since  the  entry  and  exhaust  valves 
are  not  together.  Fig.  107  shows  a  double  cylinder,  and  Plate  15B  a 
single  cylinder  Corliss  engine. 

The  Hill  or  Wheelock  Valve 

The  Hill  or  Wheelock  valve,  which  is  made  by  Messrs.  Adamson 
in  this  country,  comes  to  us  from  America,  and  it  is  claimed  to  have 
certain  advantages  over  the  Corliss  valve,  which  it  resembles  in  some 
features.  Two  types  of  the  valves  are  made,  known  respectively  as 
A  and  B.  Both  types  of  valves  are  fixed  in  castings  provided  for 
them,  forming  the  steam  chests  for  the  cylinders.  Type  A  is  slightly 
conical,  and  works  in  a  bore  of  the  same  shape,  in  the  casting  provided 
for  it.  It  is  suspended  on  trunnions,  and  has  a  semi-rotating  move- 
ment, something  on  the  lines  of  the  Corliss  valve,  motion  being  given 
to  it  by  an  eccentric  rod.  In  type  A  there  is  a  valve  for  the  entrance 
of  the  steam  to  each  side  of  the  cylinder,  and  another  valve  for  the 
egress  of  the  steam,  but  both  are  worked  by  one  eccentric,  the  exhaust 


254    STEAM   BOILERS,  ENGINES,  AND   TURBINES 


valve  spindles  being  connected  directly  to  it,  and  the  entry  valve 

spindles  being  worked  from  the  exhaust  valve  spindles,  by  latch  links. 

In  the  type  B  valve,  the  exhaust  and  entry  valves  are  in  one. 

The  arrangement  is  similar  to  that  of  type  A,  up  to  a  certain  point, 

the  valves  being  fixed  in  the  casting 
below  the  cylinder,  as  shown  in 
Fig.  100,  and  being  slightly  conical, 
and  working  in  bores  of  similar 
form  in  the  casting.  The  inside  of 
the  valves,  however,  are  flat  grid- 
irons, one  for  the  exhaust  and  one 
for  the  entry,  each  coming  opposite 
to  its  proper  port  at  the  proper 
time,  the  whole  being  worked  by 
an  eccentric  rod  from  the  crank 
shaft. 

Stop  Valves 

The  stop  valve  is  the  entry 
valve,  allowing  the  steam  to  pass 
from  the  steam  pipe,  through  which 
it  arrives  from  the  boiler,  into  the 
steam  chest  of  the  engine,  and  also 
for  admitting  the  steam  from  the 
boiler  to  the  steam  pipe.  The  stop 
valve  is  usually  a  casting  of  one  of 
the  forms  shown,  with  flanges  for 
bolting  to  a  corresponding  flange 
on  the  steam  pipe,  and  another  on 
the  steam  inlet  port  of  the  engine, 
or  the  outlet  port  of  the  boiler, 
and  it  contains  a  space,  sometimes 
spherical,  sometimes  elliptical,  and 
of  other  forms,  in  which  the  valve 
mechanism  moves.  The  casting, 
as  a  whole,  is  merely  a  continuation 

for  the  steam  from  the  pipe  into  the 


FIG.  108.— One  form  of  Stop  Valve, 
made  by  W.  H.  Willcox,  which 


inserted  between  the  Pipe  leading 
to  the  Steam  Chest  and  that  coming 
from  the  Boiler.  Steam  enters  from 
the  Boiler,  through  the  aperture  on 
the  left,  and  when  the  Valve  is  open, 
passes  up  through  the  Valve  Seat  A, 
and  out  to  the  right,  to  the  Engine. 
When  the  portion  B  is  forced  down 
on  to  A,  the  passage  of  Steam  is 
prevented,  and  its  flow  can  be  regu- 
lated by  leaving  B  closer  to  or 
farther  from  A.  In  this  Valve  B 
and  A  are  renewable. 


engine,  and  it  is  provided  with  some 

arrangement  by  which  a  barrier  can  be  introduced  in  the  path  of  the 
steam,  wholly  or  partially  preventing  its  passage.  Fig.  108  shows 
the  action  very  clearly.  In  the  sectional  drawings,  shown  in  Figs. 
109  and  110,  of  valves  made  by  Messrs.  Alley  &  Maclellan,  Fig.  109 
is  a  stop  valve  with  equilibrium  moving  member,  and  Fig.  110  is  a 


THE  STEAM  ENGINE 


255 


throttle  valve  on  something  the  same  lines.  The  moving  member  in 
the  throttle  valve  is  actuated  by  a  rod  from  the  governor,  instead  of 
by  hand.  There  are  two  forms  of  valves,  known  as  the  globe  and  the 
angle.  In  the  globe  valve,  projections  are  made  on  the  inside  of  the 
casting,  from  the  bottom  of  the  inlet  and  the  top  of  the  outlet,  the  two 
having  a  space  between  them,  in  which  a  circular  casting  called  the 
valve  seat  is  fixed,  and  the  valve  itself  moves  up  and  down  in  the 
valve  seat.  When  the  valve  is  closed  down,  as  shown  in  Figs. 
109  and  110,  the  steam  cannot  pass  through.  The  valve  is  lifted 
by  the  hand  wheel  shown  at  the  top,  which  will  be  familiar  to  every 
user  of  an  engine,  and  to  every  one  who  has  seen  an  engine.  When 


FIG.  110.— Section  of  Throttle  Valve 
with  equilibrium  moving  member, 
made  by  Messrs.  Alley  &  Maclellan. 


FIG.  109 — Section  of  a  Stop  Valve 
made  by  Messrs.  Alley  &  Mac- 
lellan. The  moving  portion 
is  of  the  equilibrium  type. 
Steam  passes  from  one  side  of 
the  Valve  to  the  other  when 
the  moving  member  is  raised. 


the  hand  wheel  is  turned,  the  screw  shown  in  the  drawing  lifts  the 
valve  off  its  seat,  and  the  steam  is  allowed  to  pass  through,  in  pro- 
portion to  the  space  provided  for  it.  In  the  angle  valve,  the  valve 
seat  is  fixed  in  the  entry  port  of  the  casting,  the  steam  turning  at 
right  angles,  as  it  passes  through  the  valve,  the  other  arrangements 
being  the  same. 

The  stop  valve  may  be  fixed  in  any  convenient  position,  and  is 
always  arranged  so  that  the  engine  man  can  handle  the  wheel  con- 
veniently. A  favourite  position  is,  the  valve  casting  being  fixed 
vertically,  and  the  wheel  standing  out  at  the  rear  of  the  engine. 

The  stop  valve  is  often  made  of  the  equilibrium  type,  as   in 


256    STEAM  BOILERS,  ENGINES,  AND   TURBINES 


Figs.  109  and  110,  that  is  to  say,  the  valve  is  in  two  halves,  so  that 
there  is  no  pressure  of  the  steam  keeping  the  valve  closed,  and 
therefore  there  is  no  difficulty  in  opening  and  closing  it. 

The  valve  body  is  usually  of  cast  iron,  and  the  valve  seat  of  gun- 
inetal.  It  is  complained  that  with  the  usual  arrangement  in  which 
the  valve  seat  is  driven  into  a  recess  in  the  cast-iron  body  of  the 
valve,  unequal  expansion  and  contraction  with  the  different  ranges 
of  temperature  to  which  the  apparatus  is  exposed,  lead  to  leakage  of 

the  steam  through  the  valve,  and  this 
has  led  to  the  design  of  several  forms 
of  valves  arranged  to  overcome  the 
difficulty. 

As  mentioned  also,  in  a  previous 
portion  of  the  chapter,  the  parts  of  the 
stop  valves  themselves  should  be  warmed 
up  before  the  valve  is  put  in  operation, 
so  that  condensation  shall  not  take 
place  in  the  valve,  or  the  steam  pipe 
beyond  it. 


The  Parallel  Slide  Stop  Valve 

One  of  the  forms  designed  to  over- 
come the  defects  of  the  ordinary  stop 
valve  is  the  parallel  slide  stop  valve, 
made  by  Messrs.  Hopkinson  &  Co.,  of 
Huddersfield,  as  shown  in  Fig.  111. 
The  arrangement  is  claimed  to  be  a 
considerable  advance  upon  the  ordi- 
nary stop  valve,  and  it  is  also  claimed 
that  all  sources  of  leakage  from  un- 


FIG.  in.-Hopkinson's  Parallel    ecLual  expansion  have  been  eliminated. 


Slide  Stop  Valve.  There  are  two  valve  seats,  as  will  be 

seen,   one   on   each   side    of   the   pipe 

forming  the  bore  of  the  valve,  the  valve  seats  being  specially 
arranged  so  that  they  are  free  to  expand,  without  creating  leakage. 
The  valve  is  closed  by  the  central  portion  sliding  in  between  the 
two  valve  seats,  and  completely  filling  up  the  steam  way.  The 
moving  portion  of  the  valve  consists  of  two  discs,  forced  outwards 
from  each  other  by  strong  springs,  the  discs  moving  over  the  faces  of 
the  valve  seats,  on  roller  bearings.  The  valve,  as  a  whole,  is  drawn 
back  bodily,  parallel  with  the  valve  seats,  into  the  space  shown 
above  in  the  olrawing,  provided  for  it,  by  the  usual  wheel  and  screw, 
as  shown.  When  the  valve  is  to  be  closed,  it  is  forced  forward  in 


-.4- 


PLATE  17A. — Horizontal  Cross-compound  Engine,  with  Rope  Drive,  for  Lancashire 

Mills. 


PLATE  17s.— Trip-valve  Gear  and  Governor,  made  by  Eastan  &  Bessemer. 

[To  face  p.  256. 


THE   STEAM   ENGINE  257 

the  same  way.  It  is  claimed,  in  addition  to  the  absence  of  leakage 
mentioned,  that  when  the  valve  is  wide  open,  there  is  a  full  bore  for 
the  steam,  equal  to  the  steam  pipe,  unchecked  by  any  projections, 
such  as  those  employed  in  the  usual  form  of  stop  valve.  When  the 
valve  is  partially  open,  the  passage  for  steam  is  crescent  shaped.  In 
addition  to  the  valve  seats  being  arranged  to  prevent  leakage,  the 
stuffing  box  or  gland  of.  the  valve  is  also  specially  constructed,  to 
provide  against  leakage.  The  passage  through  the  top  of  the  valve 
box  is  bored  to  a  conical  form  for  a  short  distance,  as  shown,  and 
then  the  usual  cylindrical  form  is  resumed.  The  conical  portion  is 
filled  with  a  bush  of  a  special  material,  which  is  claimed  to  resist 
the  action  of  water  and  high-pressure  steam.  The  space  immediately 
above  it  is  filled  with  a  preparation  of  asbestos  and  plumbago,  the 
whole  being  closed  by  the  metallic  gland.  The  screw  spindle  which 
operates  the  valve,  is  also  made  on  the  well-known  compensation 
principle,  by  which  variations  of  temperature  are  provided  for. 

A  modification  of  the  parallel  slide  stop  valve  is  the  Hopkinson- 
Ferranti  valve,  in  which  the  inlet  and  outlet  portions  of  the  valve 
are  coned,  the  valve  itself  being  fixed  in  a  throat  between  the  two 
cones.  The  steam  enters  the  valve  through  a  converging  nozzle, 
passing  into  the  valve  with  a  high  velocity,  and  passing  out  through 
a  diverging  nozzle,  in  which  the  velocity  is  lowered  to  the  normal. 


Centre   Pressure  Stop  Valve 

Another  form  of  valve  made  by  Messrs.  Hopkinson,  which  it  is 
claimed  accomplishes  practically  the  same  object,  is  shown  in  section 
in  Figs.  112,  113,  and  114,  the  figure  on  the  left  showing  the  valve 
shut,  that  in  the  middle  showing  it  partially  opened,  and  that  on 
the  right  fully  opened.  In  this  form  of  valve  there  is  a  casting 
very  similar  to  that  of  the  ordinary  stop  valve,  with  two  projections, 
one  from  the  lower  portion,  and  the  other  from  the  upper  portion, 
having  the  cylindrical  space  between  them,  as  in  the  ordinary  form 
of  valve ;  and  in  this  cylindrical  space  two  distinct  valve  seats  are 
fixed,  on  the  lines  of  the  valve  seats  described  in  connection  with 
the  parallel  slide  valve.  The  moving  portion  of  the  valve  is  in 
two  parts,  one  moving  upwards  in  closing  in  the  lower  space,  and 
coming  against  the  lower  portion  of  the  lower  valve  seat ;  and  the 
other  moving  downwards  in  closing,  and  coming  against  the  upper 
portion  of  the  upper  valve  seat.  The  two  valves  are  separately 
controlled  by  the  system  of  spindles  shown  above  the  valve  casing, 
both  of  them  being  worked  by  the  wheel  and  screw,  in  the  usual 
way.  The  upper  valve  is  the  main  valve,  and  it  is  always  opened 

s 


258     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


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THE   STEAM   ENGINE 


259 


first,  and  closed  last.  When  the  valve  is  to  be  opened,  the  upper 
valve  is  raised  from  its  seat,  as  shown  in  the  middle  drawing,  the 
lower  valve  still  preventing  the  passage  of  steam  through.  When 
the  upper  valve  has  been  fully  opened,  the  lower  valve  is  lowered,  as 
shown  in  the  figure  on  the  right,  and  the  steam  then  passes  freely 
through.  When  the  valve  is  to  be  closed,  the  lower  valve  is  first 
drawn  up  to  its  seat,  thus  shutting  off  the  steam,  the  main  valve  then 
not  having  the  steam  pressure  against  it,  is  easily  closed.  The  double 
action  is  obtained  by  the  aid  of  the  floating  bridge  above,  which  is 


FIG.  115. — Valve  made  by  Messrs.  W.  H.  Bailey  &  Co.  for  reducing  the  pressure  of 
Steam,  from  that  of  the  service,  to  what  the  Engine,  or  other  apparatus,  can 
conveniently  handle.  The  Steam  is  throttled  in  passing  through  the  Valve, 
issuing  at  a  lower  pressure. 


drawn  upwards  when  the  hand  wheel  is  turned  counter  clockwise, 
and  which  draws  up  the  carrier  attached  to  the  main  valve.  When 
the  main  valve  is  fully  opened,  the  floating  bridge  engages  with  stops 
provided  for  it,  and  then  becomes  a  fixed  nut,  the  screw  revolving 
in  it,  and  the  central  spindle  which  is  attached  to  the  lower  valve, 
then  moving  the  latter  downwards,  the  reverse  operation  taking 
place  when  the  valve  is  to  be  moved  upwards.  Another  valve  that 
is  useful  at  times  is  the  reducing  valve,  one  form  of  which  is  shown 
in  Fig.  115.  It  enables  steam  to  be  taken  from  a  high-pressure 
service  and  used  in  low-pressure  apparatus. 


260     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


Taking  the   Power  from  the   Piston 

It  has  been  explained  that  the  energy  delivered  to  the  water  in 
the  boiler  is  delivered  by  the  steam  that  is  formed  from  the  water  to 
the  moving  pistons,  in  the  cylinders  of  reciprocating  engines.  The 
next  problem  is,  the  delivery  of  the  power  from  the  piston  to  the 
machine  or  apparatus  that  is  to  be  worked.  In  the  early  Cornish 
pumping  engines,  the  arrangement  was  a  very  simple  one,  the  steam 
cylinder  stood  under  one  end  of  a  long  lever,  and  the  pump  stood 
under  the  other  end.  A  rod,  or  system  of  rods,  connected  the  piston 
with  one  end  of  the  lever  or  beam,  and  another  rod  or  system  of  rods 
connected  the  other  end  of  the  beam  with  the  pump  buckets.  As 
the  piston  moved  upwards  in  the  cylinder,  it  forced  that  end  of  the 
beam  up,  the  opposite  end  being  depressed,  and  driving  the  pump 
buckets  down  into  the  pump  in  the  suction  stroke.  When  the  piston 
descended,  as  explained  in  a  previous  part  of  the  book,  when  the  steam 
underneath  it  was  condensed,  it  pulled  down  the  end  of  the  beam 
above  it,  the  opposite  end  ascending,  and  pulling  up  the  pump  buckets, 
with  their  load  of  water,  and  delivering  it  to  the  delivery  pipe. 
With  this  arrangement  a  certain  amount  of  play  is  necessary 
between  the  ends  of  the  pump  rods  and  the  beam,  and  also  between 
the  end  of  the  rods  connecting  the  piston  with  the  beam.  This  play 
is  provided  for  by  a  loose  joint,  allowing  the  ends  of  the  rods  to 
move  round  the  ends  of  the  lever. 

For  a  large  portion  of  the  work  of  the  steam  engine,  however,  it 
is  necessary  to  convert  the  to  and  fro  motion  of  the  piston  into  rotary 
motion,  and  this  is  done  by  the  aid  of  a  crank  shaft  and  connecting 
rods.  In  a  great  many  instances,  power  is  conveniently  taken  from 
a  continuously  revolving  shaft,  such  as  a  crank  shaft,  and  is  converted 
to  to  and  fro  motion,  where  required,  in  the  machine  to  be  driven, 
by  other  mechanism ;  but  for  a  great  many  purposes,  and  particularly 
with  the  modern  tendency  to  electrical  driving,  rotary  motion  is  the 
most  convenient.  Eotary  motion  is  obtained  from  the  to-and-fro 
motion  of  the  piston,  by  attaching  to  the  end  of  the  piston  rod 
a  second  rod,  called  the  connecting  rod,  by  a  loose  joint,  and  attach- 
ing the  other  end  of  the  connecting  rod  to  the  apparatus  known  as 
a  crank.  The  piston  rod  is  attached  rigidly  to  the  centre  of  the 
piston,  and  moves  through  a  gland  or  stuffing  box  in  the  end  of  the 
cylinder,  and  is  made  only  sufficiently  long  to  project  outside  of 
the  cylinder,  when  the  piston  is  at  the  opposite  end  of  the  stroke. 
The  crank  consists  really  of  two  radii  of  a  circle,  connected  together 
by  a  cross  piece,  the  two  radii  being  attached  to  the  two  portions 
of  the  shaft  to  which  the  crank  is  to  give  motion.  In  some  smaller 
engines  the  crank  is  displaced  by  a  disc,  the  connecting  rod  being 


THE   STEAM   ENGINE  261 

attached  to  a  point  of  the  disc,  near  its  periphery.  When  the  piston 
is  at  the  commencement  of  its  stroke,  and  is  at  the  end  of  the 
cylinder  farthest  from  the  crank  shaft,  the  crank,  connecting  rod, 
and  piston  rod,  are  all  in  one  line.  As  the  piston  moves  forward, 
the  piston  rod  pushes  the  connecting  rod  forward,  and  as  the  only 
way  in  which  the  connecting  rod  can  move  is  upwards,  it  takes  a 
position  in  which  the  two  radii  forming  the  two  sides  of  the  crank 
are  slightly  inclined  to  the  horizontal.  As  the  piston  moves  forward, 
the  piston  rod  moves  on,  the  connecting  rod  following,  and  the  two 
sides  of  the  crank  shaft  making  a  gradually  increasing  angle  with  the 
horizontal.  At  half  stroke  the  two  sides  of  the  crank  shaft  make 
an  angle  of  90°  with  the  horizontal ;  and  as  the  piston  and  connecting 
rod  move  still  further  forward,  the  sides  of  the  crank  shaft  commence 
to  decrease  the  angle  with  the  horizontal  on  the  other  side,  till  at  the 
end  of  the  stroke,  the  crank  is  again  in  the  horizontal  position,  and 
the  piston  rod,  connecting  rod,  and  crank  shaft,  are  again  in  one  line. 
The  two  points  when  the  piston  rod,  connecting  rod,  and  crank,  are 
in  one  line,  are  called  the  dead  points,  and  it  is  the  rule,  whenever  an 
engine  is  stopped,  that  the  piston  should  not  be  left  in  the  position  in 
which  the  crank  is  on  either  of  its  dead  points.  It  should  be  as  near 
the  intermediate  position,  where  the  crank  is  at  an  angle  of  90°,  as 
possible. 

It  will  be  seen  that  the  linear  distance  through  which  the  crank 
pin — as  the  cross  piece  connecting  the  two  radii  of  the  crank  is  called — 
travels,  is  the  same  as  that  through  which  the  piston  travels.  In 
fact,  when  it  is  required  to  know  the  stroke  of  an  engine,  it  may  be 
measured  by  measuring  the  length  of  the  radii  of  the  crank,  and 
doubling  it. 

With  double-cylinder  engines — whether  they  are  twin  simple 
cylinders,  or  compound — it  is  usual  to  arrange  the  cranks  either  90° 
apart  on  the  crank  shaft,  or  180°.  There  are  the  usual  differences  of 
opinion  as  to  the  advantages  of  the  two  positions.  When  the  crank 
shafts  are  90°  apart,  it  is  impossible  that  both  engines  can  be  on  their 
dead  points  together,  and  therefore  there  is  no  difficulty  in  starting. 
On  the  other  hand,  where  the  crank  shafts  are  180°  apart,  the  turning 
effort  is  delivered  more  uniformly  to  the  crank  shaft. 

With  three  cylinders,  as  in  triple-expansion  engines,  the  crank 
shafts  are  arranged  120°  degrees  apart,  and  it  will  be  seen  that  there 
must  always  be  one  engine  at  least  in  a  position  to  commence  the 
turning  movement  of  the  shaft,  while  the  turning  effort  is  more  evenly 
distributed  through  the  revolution. 

The  crank  shaft  receives  the  power  from  all  the  pistons  forming 
one  engine,  no  matter  how  they  may  be  arranged.  Even  in  those 
cases  where  the  engine  cylinders  are  arranged  one  above  the  other, 
or  one  behind  the  other,  the  effort  of  all  the  cylinders  is  delivered  to 


262    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  crank  shaft,  and  the  crank  shaft  is  the  source  of  power  for  every- 
thing that  is  worked  by  the  engine,  including  its  own  valves,  governor, 
etc.  As  already  explained,  the  admission  and  exhaust  valves  of  the 
engine  are  always  worked  by  eccentrics,  and  these  take  their  motion 
from  the  crank  shaft.  Other  valves  take  their  motion  indirectly  from 
the  crank  shaft,  by  means  of  rods  working  bevelled  gear,  which 
operate  trip  mechanisms  at  proper  intervals,  but  again  it  is  the 
crank  shaft  from  which  the  motion  emanates. 

Again,  it  is  the  crank  shaft  from  which  power  is  taken  to  drive 
the  machines  or  apparatus  the  engine  is  to  work,  and  this  may  be 
done  by  directly  connecting  the  end  of  the  crank  shaft  with  the  end 
of  the  shaft  of  the  machine  to  be  driven,  as  in  the  case  of  direct-driven 
electricity  generators,  or  the  power  may  be  taken  from  the  crank  shaft 
to  the  apparatus  to  be  driven,  by  the  aid  of  gearing,  as  in  the  case  of 
winding  and  hauling  engines  for  mines,  and  other  apparatus.  In 
these  cases  the  end  of  the  crank  shaft  may  carry  either  the  pinion  of 
a  system  of  spur  and  pinion  wheels,  where  the  speed  of  the  driven 
machine  is  to  be  less  than  that  of  the  driving  engine,  or  it  may  carry 
the  spur  wheel,  where  the  speed  of  the  driven  machine  is  to  be 
greater ;  and,  again,  it  may  carry  worm  gearing  with  a  wheel  on  the 
shaft  of  the  driving  machine,  where  worm  and  wheel  driving  is 
employed. 

The  power  may  also  be  taken  from  the  crank  shaft  by  the  aid  of 
belts  or  ropes.  In  these  cases  a  pulley  is  fixed  on  the  end  of  the 
crank  shaft,  and  one  of  similar  width  on  the  end  of  the  shaft  of  the 
machine  to  be  driven,  and  the  diameters  of  the  two  pulleys  must  be 
in  the  proportion  of  the  speeds  of  the  driven  machine,  to  that  of  the 
engine.  Thus,  if  the  engine  is  running  at  400  revolutions  per  minute, 
and  the  driven  machine  is  to  run  at  100  revolutions,  the  pulley  on 
the  crank  shaft  of  the  engine  must  be  one  quarter  the  diameter  of 
that  on  the  driven  machine.  On  the  other  hand,  if  the  engine  is 
running  at  100  revolutions,  and  the  machine  is  to  run  at  400,  the 
diameter  of  the  pulley  on  the  end  of  the  crank  shaft  of  the  engine 
will  be  four  times  that  of  the  pulley  on  the  driven  machine. 

Pulleys  for  belt  driving  are  merely  hollow  cylinders,  with  a  bush 
of  the  size  of  the  shaft  on  which  they  are  to  be  fixed,  their  surfaces 
being  smooth  all  over,  and  slightly  rounded  towards  the  edges.  They 
may  be  fixed  to  the  shafts  to  which  they  are  attached  by  keys  driven 
in  between  the  shaft  and  the  boss  of  the  pulley,  or  by  screws  holding 
them.  The  power  is  transmitted  from  the  crank  shaft  of  the  engine 
to  the  shaft  of  the  driven  machine,  by  friction  between  the  belt  and 
the  two  pulleys.  The  friction  between  the  pulley  on  the  crank  shaft 
and  the  belt  lying  on  its  surface,  causes  the  belt  to  move  in  the 
direction  in  which  the  crank  shaft  is  revolving,  the  rotary  motion  of 
the  pulley  being  converted  into  linear  motion  in  the  belt,  each  portion 


THE  STEAM  ENGINE  263 

of  the  belt  travelling  from  the  pulley  on  the  crank  shaft  to  the  pulley 
on  the  driven  machine,  and  back  again.  On  the  driven  machine,  the 
friction  between  the  belt  and  the  pulley  causes  the  surface  of  the 
pulley  to  turn  in  the  direction  in  which  the  belt  is  running,  this 
causing  rotary  motion  of  the  pulley  and  of  the  shaft  to  which  it  is 
attached,  and  of  anything  the  shaft  is  driving.  There  is  always  a 
tight  side  of  a  belt  and  a  loose  side.  With  many  machines  it  is 
better  practice  to  have  the  tight  side  of  the  belt  the  lower  one.  That 
is  to  say,  the  belt  travels  from  the  under  side  of  the  pulley  of  the 
machine  to  be  driven  to  the  under  side  of  the  pulley  on  the  crank 
shaft  of  the  engine,  that  piece  of  the  belt  which  is  between  the  two 
pulleys  transmitting  the  power  from  the  engine  to  the  machine,  the 
remainder  of  the  belt  merely  acting  to  bring  successive  portions  of 
the  belt  into  the  driving  position.  Where  the  lower  side  of  the  belt 
is  the  driving  or  tight  side,  the  tendency  of  the  pull  is  to  keep  the 
driven  machine  down  on  to  its  foundations,  and  in  addition,  the 
weight  of  the  loose  portion  of  the  belt,  lying  over  the  two  pulleys  on 
the  non-driving  side,  adds  to  the  grip  of  the  belt  on  the  pulleys,  and 
improves  the  drive. 

If  a  belt  is  wet,  or  if  it  is  not  equal  to  the  power  it  is  intended 
to  transmit,  it  is  very  apt  to  slip,  and  then  the  speed  of  the  driven 
machine  is  less  than  it  should  be,  according  to  the  proportions  of  the 
two  pulleys,  and  the  speed  of  the  driving  engine.  A  belt  will  also 
slip  with  a  badly  made  joint,  and  if  it  is  not  sufficiently  tight 
between  the  two  pulleys.  When  slipping  occurs,  it  will  be  known 
by  the  heating  of  the  pulleys  over  which  it  runs,  and,  in  particular, 
that  of  the  smaller  pulley.  When  a  belt  is  running  properly,  and 
transmitting  power  as  it  should  do,  there  is  no  appreciable  heating, 
either  of  the  belt  or  of  either  of  the  pulleys ;  but  immediately  slip- 
ping commences,  the  additional  friction  between  the  belt  and  the 
surfaces  of  the  pulleys  causes  heating  which  may  easily  be  observed. 
As  a  temporary  measure,  where  a  belt  is  slipping,  resin  thrown 
between  the  belt  and  the  pulley  will  get  over  the  trouble,  but  the 
source  should  be  sought  immediately  the  opportunity  offers. 

There  is  a  certain  size  belt  for  a  certain  quantity  of  power 
delivered,  with  a  certain  speed,  and  this  is  given  from  the  formulae — 

HP  -(T-Oy 

33,000 

This  gives  the  H.P.  any  belt  will  deliver  at  any  velocity,  T  being  the 
strain  in  pounds  on  the  tight  side  of  the  belt,  t  that  on  the  slack  side, 
and  V  the  speed  of  the  belt  in  feet  per  minute,  t  is  usually  taken 
as  half  T,  as  an  average,  and  single  belts  will  stand  from  60  to  120  Ibs. 
per  square  inch,  double  belts  135  to  160  Ibs.,  so  that  taking  an  aver- 
age the  formulae  for  the  size  of  a  single  belt  becomes — 


264     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

_  33,000  x  H.P 

45  x  V 
and  for  a  double  belt — 

_  33,000  x  H.P. 
75  x  V 

W  being  the  width  of  the  belt  in  inches  in  each  case,  and  45  Ibs.  and 
75  Ibs.  the  average  values  of  T  —  t. 

When  rope  driving  is  employed,  the  surfaces  of  both  the  driving 
and  driven  pulleys  are  grooved  out,  and  a  number  of  ropes  from  two 
upwards,  according  to  the  power  to  be  transmitted,  are  laid  in  the 
grooves,  between  the  pulleys,  very  much  as  the  belts  are.  There  are 
two  methods  of  arranging  rope  driving.  In  one  a  single  rope  is 
employed,  carried  continuously  round  all  the  pulleys,  but  this  method 
is  now  very  rarely  seen.  In  the  other  method,  which  is  most  fre- 
quently employed,  there  are  as  many  endless  ropes  as  there  are 
grooves  on  the  pulleys,  the  sizes  of  the  ropes  varying  from  2J  inches 
circumference  to  6£  inches  circumference.  Ropes  are  measured  by 
their  circumference,  but  it  is  always  easy  to  reduce  them  to  approxi- 
mate diameters  by  dividing  the  circumference  by  three.  Thus  a  3-inch 
rope  is  approximately  1  inch  in  diameter.  It  will  be  remembered 
that  the  circumference  is  3f  times  the  diameter  nearly. 

Each  rope  takes  a  portion  of  the  load,  and  the  power  is  trans- 
mitted from  the  driving  to  the  driven  pulleys  by  friction  between 
the  ropes  and  the  pulleys,  just  as  by  belts.  A  complaint  is  fre- 
quently made  against  ropes,  that  the  individual  ropes  rarely  take 
their  proper  share  of  the  load,  sometimes  one  rope  having  more  than 
the  others,  and  again,  the  one  that  has  been  taking  the  heavier  load, 
losing  a  portion  of  it,  and  so  on.  This,;  it  appears  to  the  author,  is 
strictly  true  in  all  but  very  rare  instances.  If  a  system  of  driving 
by  ropes  be  examined,  it  will  always  be  seen  that  some  of  the  ropes 
are  tighter  than  others,  and  these  are  taking  the  major  portion  of 
the  load.  It  is,  the  author  believes,  almost  impossible  to  ensure  that 
each  rope  shall  take  its  own  share  of  the  load,  no  more  no  less  at 
all  times ;  but  the  remedy  for  any  trouble  that  may  arise,  appears  to 
be  the  old  one — to  have  more  ropes  than  would  be  necessary  if  it 
could  be  ensured  that  all  of  them  take  their  proper  share  of  the 
load,  and  then  the  action  appears  to  be  as  follows.  Some  of  the 
ropes  take  more  than  their  share  of  the  load  for  a  certain  time,  and 
become  gradually  elongated  in  consequence,  and  then  the  other  ropes 
that  have  not  been  subject  to  so  much  strain,  gradually  assume 
the  load,  those  which  took  it  in  the  first  instance  being  gradually 
released.  The  ropes  which  take  the  load  after  the  first  lot  have 
stretched  become  stretched  in  their  turn,  others  take  it  up,  and  so 
on,  the  whole  of  the  ropes  really  taking  their  share  of  the  work  in 


THE  STEAM   ENGINE 


265 


turn  in  this  manner,  but  it  being  necessary  that  the  individual  ropes 
shall  be  stronger  than  would  be  necessary  if  all  took  their  proper 
share  of  the  load. 

It  is  stated  also  that  the  efficiency  of  the  rope  drive  is  very  low, 
as  low  as  90  per  cent.,  while  belt  drive  is  as  high  as  98  per  cent., 
and  spur  gearing  the  same.  On  the  other  hand,  rope  driving  has 
the  great  advantage  of  being  very  smooth,  and  very  silent,  and  if  a 
little  power  is  wasted  in  transmitting  the  energy,  the  increased  cost 
of  coal  is  probably  made  up  in  other  directions.  The  formula  given 
shows  the  sizes  of  rope  for  transmitting  any  given  power. 


H.P.  = 


NPV 

3^000 


where  N  is  the  number  of  ropes,  P  the  driving  force  in  pounds,  V 
the  speed  of  the  ropes  in  feet  per  minute.  P  (the  driving  force) 
=  C2  X  x,  where  C  is  the  circumference  of  the  rope  and  x  =  6*6  for 
horizontal,  3*3  vertical,  and  9 '4  for  ropes  at  an  angle  of  45°  (Kemp). 
Worm-and-wheel  driving  was,  up  till  recently,  very  inefficient, 
but  with  the  advance  of  manufactures,  and  in  particular  with  the 
advance  in  the  working  of  machine  tools,  and  with  better  under- 
standing of  the  problem,  the  efficiency  of  worm  gearing  has  been 
considerably  increased  within  recent  years.  Worm  gearing  is  claimed 
now  to  have  efficiencies  up  to  90  per  cent., 
and  it  is  perhaps  one  of  the  most  convenient 
methods  of  transmitting  power,  where  a 
great  reduction  of  speed  is  required,  that 
is  available. 


The  Government  of  Engines 

There  are  broadly  two  forms  of  engine 
governors,  known  respectively  as  the  throttle 
governor  and  the  expansion  governor.  Both 
are  worked  either  directly  or  indirectly  from 
the  crank  shaft.  The  governor  always  con- 
sists of  a  pair  of  steel  balls,  attached  to  a 
central  rod  around  which  they  revolve,  when 
they  receive  motion  from  the  crank  shaft, 
and  they  are  arranged  to  give  motion  to  the 
rod  around  which  they  move,  so  as  to  either 
close  or  open  a  valve,  or  to  decrease  or  in- 
crease the  time  during  which  a  valve  is  open. 

The  throttle  governor,  as  explained  previously,  always  acts  upon  the 
valve  controlling  the  supply  of  steam  to  the  steam  chest.    A  common 


FIG.  116. — Pickering  Gover- 
nor. 


266    STEAM   BOILERS,  ENGINES,  AND   TURBINES 


D 


K, 


form  of  it  is  shown  in  Fig.  116.  It  is  one  that  is  employed  principally 
for  small  engines,  but  it  illustrates  the  principle  of  the  apparatus  very 
clearly.  It  is  known  as  the  Pickering  governor.  It  will  be  seen 
that  it  is  mounted  on  the  top  of  the  box  containing  the  stop  valve, 
which  is  arranged  to  be  fixed  between  the  steam  supply  pipe  and  the 
steam  chest.  A  vertical  spindle  rises  from  the  top  of  the  valve  box, 
and  carries  at  its  head  three  flat  springs,  on  which  are  three  steel  balls, 

the  three  springs  being  also  attached 
at  their  lower  ends,  so  that  they  can 
slide  up  the  spindle.  The  spindle 
at  its  lower  end  in  the  box  controls 
the  motions  of  the  valve,  allowing 
steam  to  pass  to  the  steam  chest. 
The  valve  can  also  be  controlled  by 
the  valve  wheel,  as  usual.  In  other 
forms  of  governor  there  is  a  spiral 
spring  on  the  central  spindle,  against 
which  the  balls,  as  they  revolve, 
have  to  work.  The  small  pulley 
shown  in  the  Pickering  governor,  on 
which  a  strap  from  a  pulley  on  the 
crank  shaft  runs,  gives  motion  to 
the  spindle,  and  through  it  to  the 
steel  balls.  As  the  balls  revolve 
they  move  outwards  by  centrifugal 
force,  and  as  they  move  out,  they 
tend  to  depress  the  central  spindle, 
this  tending  to  close  the  valve. 
When  the  engine  is  running  at  its 
normal  speed,  the  steel  balls  revolve 
round  the  spindle  at  a  certain  dis- 
tance, the  flat  springs  being  bent 
to  a  certain  curve.  If  the  engine 
increases  its  speed,  as  say  when 
the  load  is  decreased,  the  balls 
move  at  an  increased  speed,  and 
move  further  outwards,  owing  to 
the  increased  centrifugal  force,  this 
down,  and  to  partially  close  the 
of  the  steam  in  the  steam  chest. 


FIG.  117. — Section  of  Proell's  Gover- 
nor, made  by  Messrs.  Isaac  Storey. 
P,  P2  are  the  Governor  Balls,  held, 
when  at  rest,  in  the  Hanging  Straps, 
H!  H2.  G  is  the  Valve  Spindle,  and 
A  a  Tube  in  which  the  Spiral  Spring 
is  enclosed.  When  the  Engine  is 
working,  G  revolves,  carrying  Hj  H2 
and  Pj  P2  round.  Pl  P2  fly  out, 
forcing  S  up  and  compressing  the 
Spiral. 


tending  to  push  the  spindle 
valve,  decreasing  the  pressure 
On  the  other  hand,  if  the  speed  of  the  engine  is  lowered,  owing, 
say,  to  an  increased  load,  the  balls  revolving  at  a  lower  speed 
fall  inwards  towards  the  spindle,  this  causing  the  valve  to  rise, 
and  to  let  more  steam  into  the  steam  chest,  increasing  the  pres- 
sure behind  the  piston.  Fig.  117  shows  the  Proell  governor,  in 


THE  STEAM  ENGINE 


267 


which  a  spiral  spring  opposes  the  centrifugal  force  of  the  governor 
balls. 

It  has  been  shown  by  the  exhaustive  experiments  of  Captain 
Sankey  and  others,  that  the  throttle  valve  is  only  economical  under 
certain  conditions,  as  with  very  light  load,  and  when  the  load  is 
beyond  a  certain  proportion  of  the  possible  full  load.  Between  these 
the  expansion  governor,  to  be  described,  more  accurately  controls  the 


FIG.  118. — Wilson  Hartnell's  Expansion  Governor,  made  by  Messrs.  Marshall.  The 
link  motion,  described  on  page  247,  is  seen  on  the  right.  The  position  of 
the  Governor  Balls  controls  the  position  of  the  Expansion  Valve  Rod,  with 
reference  to  the  Eccentric  Hod,  and  through  it  the  time  the  Slide  Valve  is  open. 

supply  of  steam  to  the  engine,  in  accordance  with  the  work  the 
engine  is  doing. 

It  will  be  understood  that  the  supply  of  steam  to  the  engine  is 
controlled,  in  both  cases,  after  an  increase  or  decrease  of  load  has 
taken  place.  The  object  of  the  governor  is  to  accurately  proportion 
the  supply  of  steam  in  the  engine  to  the  work  the  engine  is  perform- 
ing. Thus,  if  the  engine  is  only  working  at  half  load,  it  should  only 


268    STEAM   BOILERS,  ENGINES,   AND    TURBINES 


take  a  little  more  than  half  the  steam  it  would  at  full  load,  the 
increase  with  the  half  load  being  due  to  the  larger  proportion  which 
the  steam,  required  to  overcome  the  friction  of  the  engine  itself, 
bears  to  that  required  for  half  the  load,  than  to  that  required  for 
full  load. 

Throttle  governing  differs  from  expansion  governing  in  that  the 
throttle  governor  controls  the  pressure  at  which  the  steam  enters  the 
steam  chest,  but  does  not  attempt  to  control  the  time  during  which 
the  entry  valve  to  the  steam  cylinder  is  open.  The  pressure  of  the 
steam  entering  the  steam  chest  is  controlled  by  opening  the  valve 
more  or  less.  With  the  valve  partially  closed,  not  so  much  steam 

can  pass  through,  and  therefore 
steam  does  not  enter  the  steam 
chest  at  the  same  rate,  other 
conditions  being  the  same,  and 
the  effect  is  a  lowered  pressure. 
The  result  of  partially  closing 
the  valve  is  the  same  so  far  as 
pressure  is  concerned,  as  of 
interposing  a  length  of  steam 
pipe  between  the  supply  pipe 
and  the  engine. 

In  the  expansion  governor, 
the  pressure  of  steam  entering 
the  steam  chest  is  not  con- 
trolled at  all,  but  the  portion 
of  the  stroke  during  which 
steam  enters  the  cylinder  is 
controlled  according  to  the  load 

the  engine  is  doing. 
FIG.   119. — Expansion  Governor  made  by  T«   *i.« 

Messrs.  Coitman.    C  is  the  Eccentric  Zf .  the  expansion  governor, 

Bod;  A  is  the  Slide  Valve  Bod;  B  is       01   which  Tig.    118,   the   gover- 

the  Arc  of  the  link  motion.  nor  introduced  by  Mr.  Wilson 

Hartnell,  is   a  good   example, 

there  is  the  same  pair  of  balls,  though  they  are  usually  much  heavier 
than  those  in  the  throttle  governor  for  the  same  sized  engine,  but  the 
rod,  which  is  much  stronger  with  the  throttle  governor,  is  made  to 
control  the  travel  of  the  slide  valve,  as  shown  in  Fig.  118.  The  action 
of  the  governor  is  very  similar  to  that  of  the  throttle  governor.  It 
receives  motion  by  means  of  a  strap,  or  in  some  cases  by  a  rod  and  bevel 
gearing  from  the  crank  shaft,  and  its  balls  move  outwards  by  centri- 
fugal force,  just  as  the  throttle  governor's  balls  do,  and  it  moves  its 
vertical  rod  more  or  less  as  the  balls  move  out  or  in,  these  again 
moving  in  accordance  with  the  increase  or  decrease  of  speed  of  the 
engine,  but  the  motion  of  the  rod  controls  the  position  of  the  valve 


THE   STEAM   ENGINE 


269 


rod  controlling  the  travel  of  the  slide  with  reference  to  the  eccentric 
rod,  by  moving  the  arc  of  the  link  motion.  With  increased  speed  of 
the' engine,  the  travel  of  the  slide  is  reduced,  the  steam  only  entering 
the  cylinder  for  a  smaller  portion  of  the  stroke,  and  with  decreased 
speed  of  the  engine  the  travel  of  the  slide  is  increased,  giving  steam 
for  a  longer  portion  of  the  stroke.  Fig.  119  shows  another  form 

of  expansion  governor,  by  Messrs. 
H.  Coltman,  in  which  the  action 
of  the  governor  on  the  link  motion 
is  very  clearly  shown. 

Both  expansion  and  throttle 
governors  are  often  fixed  directly 
on  the  crank  shaft  itself.  In 
those  cases  there  is  usually  a  disc 


FIG.  120. — Proell  Governor,  made  by  Messrs.  Isaac 
Storey,  fixed  on  the  end  of  the  Crank  Shaft, 
and  controlling  the  Throttle  Valve  above,  by 
means  of  the  Vertical  Rod  shown. 


FIG.  121. — Expansion  Shaft  Governor,  made  by 
Messrs.  Ransome,  Sims,  &  Co.,  for  High- 
speed Vertical  Engines.  The  parts  of  the 
Governor  are  enclosed  in  the  Box  shown. 


carried  by  the  crank  shaft,  on  which  the  governor  balls  or  their 
equivalent  are  mounted,  and  from  which  motion  is  conveyed  to  the 
eccentric  controlling  the  slide  valve  by  gearing.  In  the  governor, 
which  is  worked  in  conjunction  with  the  drop  valve  expansion  gear 
described  on  page  250,  the  time  during  which  the  eccentric  rod  K, 
in  Fig.  103,  engages  with  the  lever  opening  the  steam  entry  valve  is 
controlled  by  the  governor  in  the  same  manner  as  in  the  slide-valve 
expansion  governor.  With  increased  speed  the  eccentric  rod  engages 


270    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

for  a  shorter  time  with  the  valve  lever,  the  valve  thence  being  open 
for  a  shorter  time,  and  with  decreased  speed,  the  rod  being  longer  in 
contact.  Fig.  120  shows  a  Proell  governor  driven  from  the  crank 
shaft  and  controlling  a  throttle  valve  above.  Fig.  120  shows  a 
governor  fixed  on  the  end  of  the  crank  shaft,  and  controlling  the 
expansion. 

The  Indicator 

The  indicator  is  the  apparatus  employed  to  find  the  mean  effective 
pressures  in  engine  cylinders.     Fig.  122  shows  one  form  of  it,  made 


FIG.  122. — Crosby's  Steam-engine  Indicator.     The  Cylinder  on  the  left  repeats  the 
Steam  Pressure  in  the  Engine  Cylinder,  and  that  on  the  right  carries  the  Paper. 

by  Messrs.  Crosby.  It  consists  of  a  small  cylinder  with  a  small 
piston,  and  a  piston  rod  inside,  and  another  cylinder  arranged  to  re- 
volve on  its  axis  once  in  the  time  Occupied  by  one  stroke  of  the  engine 
that  is  being  indicated,  and  at  exactly  the  same  speed,  and  the  piston 


THE  STEAM   ENGINE 


271 


and  the  cylinder  together  reproduce  what  is  going  on  in  the  engine 
cylinder,  though  in  a  different  manner.  On  the  outside  of  the  small 
revolving  cylinder  is  wrapped  a  piece  of  paper,  squared  for  preference, 
as  it  renders  the  measurements  easier,  and  a  pencil  attached  to  an  arm 
worked  by  the  piston  bears  on  the  surface  of  the  paper.  As  long  as 
the  pressure  in  the  steam  indicator  cylinder  is  constant,  as  when  it  is 
open  to  the  atmosphere,  the  pencil  merely  runs  round  the  cylinder, 
making  a  line  that  is  straight  when  the  paper  is  unrolled,  but  when  the 
pressure  in  the  piston  in  the  indicator  cylinder  varies,  the  position  of 
the  pencil  varies  in  unison  with  it,  the  result  being  a  curved  and  some- 
times irregular  line.  The  indicator  cylinder  is  connected  by  a  small 
steam  pipe  to  the  engine  cylinder,  small  cocks  being  provided  in  the 
cylinder  walls  for  the  purpose,  and  when  connection  is  made,  the 
pressure  of  the  steam  in  the  engine  cylinder  is  reproduced  in 
the  indicator  cylinder.  The  piston  of  the  indicator  cylinder  does 


FIG.  123. — Examples  of  Indicator  Cards  taken  from  a  Triple-expansion  Engine.  The 
Cards  show  the  pressures  in  the  High-pressure,  One-pressure,  and  two  Low- 
pressure  Cylinders,  also  the  action  of  the  Cut-off  at  different  parts  of  the  Engine. 
The  Cards  in  the  middle  show  the  pressure,  with  different  Cut-offs. 

not  move  in  the  same  way  as  the  piston  of  the  engine  cylinder  does. 
It  takes  up  a  position  within  its  own  cylinder  in  accordance  with 
the  pressure  behind  it.  The  motion  of  the  piston  is  opposed  by  a 
coiled  spring  on  the  piston  rod,  and  the  motion  allowed  to  the  piston 
is  exactly  proportional  to  the  pressure  exerted  by  the  steam.  When 
an  engine  is  to  be  indicated,  connection  is  made  to  the  steam  space 
in  the  engine  cylinder  behind  the  piston,  and  arrangements  are  also 
made  to  revolve  the  paper  carrying  cylinder  in  unison  with  the  motion 
of  the  engine  piston,  usually  by  a  string  attached  to  some  moving 
part  of  the  engine  and  to  the  indicator  cylinder.  The  revolution  of 
the  indicator  cylinder  is  also  opposed  by  a  spring.  When  all  is  ready, 
the  engineer  first  obtains  his  atmospheric  line  upon  the  indicator  paper 
by  revolving  the  cylinder,  with  the  pencil  bearing  against  the  paper, 
and  with  the  indicator  cylinder  open  to  the  atmosphere.  Connection 
is  then  made  to  the  engine  cylinder,  and  the  apparatus  is  allowed  to 


272     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

work.  The  piston  is  forced  outwards  in  the  indicator  cylinder  when 
the  stroke  commences,  and  gradually  recedes  as  the  pressure  falls, 
the  pencil  making  a  line  upon  the  paper  in  accordance  with  this. 
The  pencil  follows  pressure  behind  the  piston  of  the  engine  right 
to  the  end  of  the  stroke,  and  during  the  return  stroke,  the  line 
formed  on  the  paper  giving  the  pressure  of  the  steam  inside  the 
cylinder,  above  or  below  atmospheric  pressure,  at  each  instant.  The 
steam  and  paper  cylinders  are  in  one  in  the  older  forms  of  indicators. 
Fig.  123  show  indicator  cards,  as  they  are  called,  taken  from 
various  engines.  In  some,  it  will  be  seen,  the  return  pressure  is 


pi 

FIG.  124. — One  form  of  Planimeter  made  by  Messrs.  Crosby. 

below  the  atmospheric  line.  This  means  that  the  engine  was  working 
with  a  condenser.  In  others  the  return  stroke  shows  pressures 
appreciably  above  the  atmospheric  line.  This  shows  back  pressures 
appreciably  above  the  atmosphere.  In  all  cases  the  mean  of  all  the 
pressures  throughout  the  stroke  is  taken,  and  the  result  is  the  figure 
used  in  the  calculations  given  on  p.  218. 


FIG.  125.— Another  form  of  Planimeter  made  by  Messrs.  Crosby. 

It  will  be  noticed  that  the  first  portion  of  the  line  representing 
the  pressure  is  parallel  with  the  atmospheric  line.  This  represents 
the  portion  of  the  stroke  during  which  the  cylinder  was  open  to  the 

Eressure  of  the  steam  chest ;  and  in  late  cut-offs,  it  will  be  seen,  the 
mgth  of  this  portion  is  large,  compared  to  the  whole  stroke,  while 
in  early  cut-offs  it  is  small.  To  an  expert  the  indicator  tells^  nearly 
everything  he  wants  to  know  about  the  engine,  how  it  is  working, 
what  steam  it  is  using,  etc.  Figs.  124  and  125  show  planimeters, 
instruments  for  transferring  the  curves  of  indicator  cards  to  larger 
paper,  and  measuring  the  quantities  easily  and  quickly. 


THE  STEAM   ENGINE  273 


Steam   Pipes 

Pipes  are  employed  for  conveying  the  steam  from  the  boiler  to 
the  engine,  and  from  the  engine  to  the  condenser,  or  to  the  exhaust. 
Steam  pipes  are  made  usually  of  wrought  iron  or  steel,  and  they 
must  be  of  a  certain  size  in  order  that  they  may  convey  the  steam 
from  the  boiler  to  the  engine  without  throttling,  and  also  from  the 
engine  to  the  exhaust.  The  remarks  that  have  been  made  about  the 
friction  of  fluids  upon  the  walls  of  pipes  through  which  they  are 
passing,  apply  equally  to  steam.  The  passage  of  steam  through 
steam  pipes  causes  friction  upon  the  walls  of  the  pipe,  and  in  so 
doing,  robs  the  steam  of  a  portion  of  the  pressure  that  was  delivered 
to  it  in  the  boiler.  Further,  the  friction  depends  directly  upon  the 
surface  over  which  the  steam  rubs,  this  depending  upon  the  length 
of  the  pipe  and  the  internal  surface,  and  it  also  depends  upon  the 
square  of  the  velocity  of  the  steam.  The  same  thing  applies  here  as 
has  been  mentioned  before.  If  the  steam  is  confined  in  too  small  a 
pipe,  its  velocity  is  increased,  and  though  the  internal  surface  of  the 
pipe  is  less  than  with  a  larger  pipe,  the  increased  friction,  owing  to 
the  increased  velocity,  is  very  much  greater.  Hence  it  is  of  im- 
portance that  the  pipe  should  be  of  sufficient  diameter  to  carry  the 
steam  without  undue  friction.  The  distribution  of  steam  in  steam 
pipes  has  been  compared,  not  inaptly,  to  the  distribution  of  electricity 
by  means  of  cables.  Steam  has  been  used  for  a  great  many  more 
years  than  electricity,  and  therefore  it  looks  a  little  strange  for  steam 
phenomena  to  be  illustrated  by  the  aid  of  practice  in  electricity ;  but 
the  arrangements  for  distributing  electricity  are  so  much  simpler,  as 
a  rule,  than  for  distributing  steam,  and  have  been  so  much  more  fully 
worked  out,  that  the  comparison  is  not  at  all  inapt.  On  the  other 
hand,  it  should  be  noted  that  the  differences  between  heat  and 
electricity  are  strongly  accentuated  in  the  matter  of  the  distribution 
of  steam,  as  against  that  of  electricity.  The  loss  of  pressure  when 
steam  passes  through  a  steam  pipe  has  been  compared  to  the  loss  of 
pressure  which  takes  place  when  an  electric  current  passes  through 
a  cable;  but  although  this  comparison  is  strictly  correct  up  to  a 
certain  point,  it  has  the  very  important  difference  that  the  energy 
lost  in  the  conductor,  owing  to  the  resistance  of  the  conductor,  is 
actually  lost  so  far  as  the  useful  application  of  the  electric  current 
is  concerned,  while  there  is  no  loss  of  energy  due  to  the  friction  of 
the  steam  in  the  pipes.  If  there  is  a  loss  of  one  volt,  or  five  volts 
in  an  electrical  distribution  service,  or  whatever  it  may  be,  there  is 
that  much  less  electrical  energy  to  use  for  lighting,  or  power,  or 
whatever  the  electricity  may  be  employed  for.  And  the  reason  for 
this  is,  that  the  energy  absorbed  by  the  resistance  of  the  electrical 


274     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

conductor  is  converted  into  heat,  which  not  only  plays  no  useful  part 
in  the  distribution  of  the  current,  but  actually  adds  to  the  resistance 
of  the  conductor,  and  may  lead  to  other  troubles,  such  as  deteriora- 
tion of  the  insulating  envelope.  On  the  other  hand,  though  the 
friction  of  the  steam  on  the  walls  of  the  steam  pipe,  and  on  the 
steam  passages  of  valves,  etc.,  also  generates  heat,  it  involves  no 
loss.  It  is  merely  a  transference  of  heat  from  the  steam,  in  the  form 
of  pressure,  to  heat  in  the  steam  pipe  and  in  the  steam  itself,  and  it 
is  claimed  by  steam  engineers  that  the  heat  so  liberated  tends  to 
superheat  the  steam.  Put  in  another  way,  the  energy  is  lost  as 
pressure,  the  steam  expanding  in  accordance  with  the  laws  given  in 
the  first  chapter,  but  the  energy  is  regained  in  the  form  of  heat 
delivered  to  the  steam  of  the  lower  pressure  in  the  form  of  superheat. 
At  the  same  time,  it  will  be  understood  that  there  is  a  limit  to  the 
size  to  which  the  steam  pipes  may  be  reduced,  and,  as  usual,  practice 
has  determined  it  by  the  velocity  of  the  steam  that  is  found  most 
economical  in  practice.  A  velocity  of  steam  of  6000  feet  per  minute, 
equal  to  100  feet  per  second,  is  that  usually  employed,  though  in 
marine  work,  velocities  up  to  150  feet  per  second  are  often  usefully 
employed.  For  the  first  velocity  named,  100  feet  per  second,  the 
loss  of  pressure  has  been  worked  out  by  Prof.  Unwin  and  others, 
and  is  given  by — 


where  p  is  the  loss  in  pressure  of  the  steam  in  pounds  per  square  inch 
due  to  the  friction  of  the  steam  through  the  pipes,  K  is  the  coefficient 
of  friction  given  as  0'0026  and  0'0027  for  steam,  D  is  the  weight  of 
steam  per  cubic  foot,  di  is  the  diameter  of  the  pipe  in  inches,  w  is 
the  flow  of  steam  in  pounds  per  minute,  and  L  is  the  length  of  the 
pipe  in  feet. 

Substituting  the  value  of  K,  0'0027,  the  formula  becomes — 

p  =  0'00013l(l 

And  the  weight  of  steam  passing  with  a  difference  of  pressure,  p, 
between  the  two  ends  of  any  pipe,  is  given  by  the  formula — 

w  =  87 


The  weight  of  steam  per  minute  that  passes  through  pipes  of  given 
size  has  been  calculated,  and  is  given  in  the  tables  on  pages  276 
and  277,  for  a  loss  of  pressure  in  the  pipe  of  1  Ib.  per  square  inch 


THE   STEAM   ENGINE  275 

As  will  be  seen,  the  figures  are  given  for  different  sizes  of  pipes,  and 
for  lengths  of  each  pipe  equal  to  240  diameters  of  the  pipe  itself, 
also  with  different  initial  steam  pressures. 

Elbows  in  pipes,  globe  valves,  and  square- ended  entrances  to 
pipes,  all  offer  resistance  to  the  passage  of  steam,  and  it  is  convenient 
to  reckon  the  resistance  offered  by  these  as  equal  to  that  of  a  certain 
length  of  pipe  of  the  diameter  of  the  steam  way  through  the  valve, 
or  elbow,  or  fitting.  For  globe  valves,  and  the  resistance  offered  by 
the  entrance  to  a  pipe,  it  is  usual  to  take  a  resistance  equal  to  that 
of  a  pipe  of  the  same  diameter,  and  of  a  length  sixty  times  the 
diameter,  and,  for  an  elbow,  forty  times  the  diameter.  The  discharge 
of  steam  in  pounds  per  minute*  through  any  pipe,  with  a  given  drop 
in  pressure,  has  been  calculated,  and  also  the  drop  in  pressure  in 
pounds  per  square  inch,  corresponding  to  any  given  drop,  have  also 
been  calculated,  and  they  are  given  in  the  annexed  tables. 

On  the  other  hand,  one  of  the  great  evils  to  which  steam  is 
exposed  in  its  passage  through  steam  pipes  is  the  loss  of  heat  owing 
to  radiation  from  the  external  surface  of  the  pipe,  and  this,  it  will  be 
evident,  will  depend  directly  upon  the  extent  of  the  surface  of  the 
pipe,  and  will  increase  in  direct  ratio  to  the  diameter.  Hence,  it  is 
a  disadvantage  to  employ  too  large  a  pipe,  because  the  loss  of  heat 
leads  to  condensation  of  some  part  of  the  steam,  and  this  leads  to 
a  double  evil — loss  of  the  steam  itself  as  a  useful  agent  for  power, 
and  presence  of  water  in  the  steam  system  that  must  be  got  rid 
of,  or  that  will  lead  to  serious  trouble. 


Water  Hammer 

By  water  hammer  is  meant  the  effect  that  is  produced  in  steam 
cylinders,  and  in  steam  pipes,  by  the  presence  of  water,  the  water 
being  driven  forward  by  a  rush  of  steam.  Thus,  in  a  steam  cylinder, 
if  water  is  present,  and  steam  is  suddenly  allowed  to  pass  into  the 
cylinder  in  a  large  quantity,  the  water,  which  is  practically  incom- 
pressible, acts  exactly  as  a  hammer  driven  with  great  violence  against 
the  end  of  the  cylinder,  and  has  often  been  known  to  drive  off  the 
cylinder  cover.  Similarly,  when  engines  are  standing,  and  steam  is 
present  in  the  steam  pipes  connecting  them  with  the  boiler,  and 
steam  be  suddenly  allowed  to  drive  through  the  steam  pipes,  if  water 
be  present  in  them,  it  is  driven  up  against  the  surfaces  of  the  pipes 
and  against  any  projecting  surfaces,  as  where  pipes  make  a  bend,  and 
so  on,  the  result  being  that  joints  are  seriously  weakened  and  pipes 
are  sometimes  burst.  The  water  being  practically  incompressible, 
is  driven  forward  at  the  velocity  of  the  steam,  hence  the  enormous 
energy  expended. 


276    STEAM   BOILERS,  ENGINES,   AND   TURBINES 


t—  t-  CDOCOOOt- 
T-IOO 


lUl 

ag.a-2 

•si'Ss 

mi 


THE   STEAM   ENGINE 


277 


TABLE  XXII. 
FLOW  OF  STEAM  THROUGH  PIPE. 


LENGTH  OF  PIPE  ONE  THOUSAND  FEET. 


Discharge  in  pounds  per  minute  corresponding  to  drop  in  pressure  on  right  for  pipe  diameters 
in  inches  in  top  line. 


Diameter  ... 

12  ins. 

10  ins. 

8  ins. 

6  ins. 

4  ins. 

3  ins. 

2J  ins. 

2  ins. 

.li  ins. 

lin. 

Discharge 

2328 

1443 

799 

371-0 

123-0 

55-9 

28-8 

18-1 

6-81 

2-52 

2165 

1341 

742 

344-0 

114-6 

51-9 

27-6 

16-8 

6-52 

2-34 

1996 

1237 

685 

318-0 

106-9 

47-9 

26-4 

15-5 

6-24 

2-16 

1830 

1134 

628 

292-0 

97-0 

43-9 

25-2 

14-2 

5-95 

1-98 

1663 

1031 

571 

265-0 

88-2 

39-9 

24-0 

12-9 

5-67 

1-80 

1580 

979 

542 

252-0 

83-8 

37-9 

22-8 

12-3 

5-29 

1-71 

1497 

928 

514 

239-0 

79-4 

35-9 

21-6 

11-6 

5-00 

1-62 

1414 

876 

485 

226-0 

75-0 

33-9 

20-4 

10-9 

4-72 

1-53 

1331 

825 

457 

212-0 

70-6 

31-9 

19-2 

10-3 

4-43 

1-44 

1248 

873 

428 

199-0 

66-2 

23-9 

18-0 

9-68 

4-15 

1-35 

1164 

722 

400 

186-0 

61-7 

27-9 

16-8 

9-03 

3-86 

1-26 

1081 

670 

371 

172-0 

57-3 

25-9 

15-6 

8-38 

3-68 

1-17 

908 

619 

343 

159-0 

52-9 

23-9 

14-4 

7-74 

3-40 

1-08 

915 

567 

314 

146-0 

48-5 

21-9 

13-2 

7-10 

3-11 

0-99 

832 

516 

286 

132-0 

44-1 

20-0 

12-0 

6-45 

2-83 

0-90 

748 

464 

257 

119-0 

39-7 

18-0 

10-8 

5-81 

2-55 

0-81 

665 

412 

228 

106-0 

35-3 

16-0 

9-6 

5-16 

2-26 

0-72 

582 

361 

200 

92-6 

30-9 

14-0 

8-4 

4-52 

1-98 

0-63 

TABLE   XXIII. 
FLOW  OF  STEAM  THROUGH  PIPE. 


LENGTH  OF  PIPE  ONE  THOUSAND  FEET. 


Drop  in  pressure  in  pounds  per  square  inch  corresponding  to  discharge  on  lelt ;  densities  and 
corresponding  absolute  pressures  per  square  inch  in  first  two  lines. 


Density 

0-208 

0-230 

0-284 

0-328 

0-401 

0-443 

0-506 

0-548 

Pressure      ... 

90 

100 

125 

150 

180 

200 

230 

250 

Drop 

18-10 

16-4 

13.3 

ll'l 

9-39 

8-50 

7-44 

6-87 

15-60 

14-1 

11-4 

9-60 

8-09 

7-33 

6-41 

5-92 

13-3 

12-0 

9-74 

8-18 

6-90 

6-24 

5-47 

5-05 

11-1 

10-0 

8-13 

6-83 

5-76 

5-21 

4-56 

4-21 

9-25 

8-36 

6-78 

5-69 

4-80 

4-34 

3-80 

3-51 

8-33 

7-53 

6-10 

5-13 

4-32 

3-91 

3-42 

•  3-16 

7-48 

6-76 

5-48 

4-60 

3-88 

3-51 

3-07 

2-84 

6-67 

6-03 

4-88 

4-10 

3-46 

3-13 

2-74 

2-53 

5-91 

5-35 

4-33 

3-64 

3-07 

2-78 

2-43 

2-24 

5-19 

4-69 

3-80 

3-19 

2-69 

2-44 

2-13 

1-97 

4-52 

4-09 

3-31 

2-78 

2-34 

2-12 

1-86 

1-72 

3-90 

3-53 

2-86 

2-40 

2-02 

1-83 

1-60 

1-48 

3-32 

3-00 

2-43 

2-04 

1-72 

1-56 

1-36 

1-26 

2-79 

2-52 

2-04 

1-72 

1-45 

1-31 

1-15 

1-06 

2-31 

2-09 

1-69 

1-42 

1-20 

1-08 

0-949 

0-877 

1-87 

1-69 

1-37 

1-15 

0-97 

0-878 

0-769 

0-710 

1-47 

1-33 

1-08 

0-905 

0-762 

0-690 

0-604 

0-558 

1-13 

1-02 

0-828 

0-695 

0-586 

0-531 

0-456 

0-429 

278     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Arrangement  of  Steam  Pipes 

The  arrangement  of  the  pipes  of  a  steam  system  must  be  such  as 
will  provide  for  getting  rid  of  the  water  that  is  formed  by  condensa- 
tion and,  as  explained  below,  for  the  expansion  and  contraction  of 
the  pipes.  The  usual  arrangement  is,  a  steam  pipe  rises  from  the 
top  of  each  boiler,  and  is  connected  to  the  common  steam  main,  by 
a  proper  flanged  steam-tight  joint,  a  stop  valve  being  fixed  between 
the  boiler  and  the  steam  main.  It  is  of  advantage  to  arrange  that 
the  stop  valve  between  the  boiler  and  the  main  shall  close  automatic- 
ally, in  case  anything  happens  to  the  steam  connection,  to  prevent 
the  rush  of  steam  into  each  particular  boiler  in  case  of  accident.  The 
engines  are  supplied  by  pipes  from  the  steam  main,  and  these  should 
always  be  taken  from  the  upper  side  of  the  main,  and  steam  separators 
should  be  fixed  between  the  branch  steam  pipes  and  each  engine. 
Provision  must  be  made  for  draining  the  steam  system,  and  this  may 
conveniently  be  done  by  extending  the  main  steam  pipe  a  little 
beyond  the  engines  to  be  supplied,  by  a  pipe  specially  for  the  purpose, 
ending  in  a  steam  trap,  and  a  pipe  from  this  steam  trap  may  be 
carried  back  to  the  boiler  below  the  water-line,  and  the  steam 
separators  from  all  the  engines  may  drain  into  this  pipe  and  any 
other  traps  that  are  in  the  system. 

Pockets  in  the  steam  ^piping  and  places  such  as  the  top  of  valves 
where  condensed  water  may  settle  must  be  avoided  as  much  as 
possible,  because,  though  the  water  may  remain  in  the  pocket  quiescent 
under  ordinary  working  conditions,  when  the  engines  beyond  the 
pocket  call  for  a  sudden  increase  of  steam,  the  action  that  has  been 
described,  of  any  gas  passing  over  a  body  of  water,  will  draw  up  the 
condensed  water  in  the  pocket  and  will  carry  it  before  the  steam  at 
the  velocity  of  the  steam,  and  possibly  deliver  it  into  the  engine,  with 
the  attendant  troubles.  Lodgment  on  the  top  of  valves  leads  to 
danger  of  a  similar  kind  when  the  valves  are  opened. 

The  steam  pipe  should  slightly  incline  in  the  direction  in  which 
the  steam  is  to  travel,  so  that  any  condensed  water  that  is  formed 
will  drain  naturally  towards  the  steam  trap  at  the  end  of  the  system, 
and  will  keep,  when  not  disturbed,  to  the  lower  part  of  the  pipe. 
When  it  is  necessary  to  raise  the  pipe  to  supply  a  certain  engine, 
a  steam  trap  should  be  Qxed  at  the  lowest  part  of  the  portion  which 
rises,  so  that  any  water  that  is  formed  may  be  drained  away. 

Steam  pipes  are  jointed  by  the  aid  of  flanges  cast  on  their 
ends,  the  two  flanges  of  adjacent  pipes  being  butted  together,  and 
bolted  closely  with  some  substance  between  the  two  flanges  that 
will  prevent  the  egress  of  steam.  Substances  that  are  employed 
for  this  purpose  are  rubber  rings,  lead  rings,  rings  formed  of  asbestos 


THE   STEAM   ENGINE  279 

and  rubber,  and  rings  formed  of  corrugated  metal.  It  is  important 
that  the  pipes  shall  be  properly  supported,  so  that  their  weight 
shall  be  taken  off  the  joints.  It  will  be  understood  that  the 
weight  of  a  large  pipe  constantly  upon  the  bolts  upon  which  the 
joints  between  the  two  lengths  of  pipes  depends,  will  tend  to  pull 
the  flanges  away  from  each  other  in  one  part  of  the  pipe,  and  to  crush 
the  material  used  for  the  joint  at  another  part  of  the  pipe,  the  result 
being  a  possible  leakage  of  steam.  Steam  pipes  are  supported  by 
brackets  fixed  to  the  walls  or  hangers  from  beams,  or  in  any  con- 
venient way,  the  supports  being  merely  rings  made  in  two  halves  so 
that  they  can  be  clasped  around  the  pipe,  the  ring  being  held  by 
rods  from  above  or  by  the  brackets  from  the  sides,  or  in  any  con- 
venient way. 

The  ring  main  system  of  steam  pipes  was  at  one  time  introduced 
into  some  of  the  electricity  generating  stations,  but  has  now  been 
practically  abandoned.  The  idea  of  the  arrangement  was  similar  to 
that  of  the  ring  system  of  electrical  distribution  employed  by  some 
of  the  earlier  electricity  supply  companies  in  London,  and  which 
ensured  two  chances  of  supply  to  any  particular  group  of  consumers. 
A  ring  of  steam  pipes  was  taken  round  the  boilers  and  the  engines, 
which  were  fixed  back  to  back,  and  it  was  supposed  that  in  case  of 
anything  happening,  there  were  two  chances  of  getting  steam  to  the 
engines.  Practice  has  shown,  however,  that  the  two  chances  are  of 
breakdown  rather  than  of  increased  service,  and,  meanwhile,  the  more 
•than  double  length  of  steam  main  gives  more  than  double  the  loss  by 
radiation. 

There  is  another  important  matter  in  connection  with  steam  pipes, 
and  that  is  that  they  are  exposed  to  the  expansion  and  contraction 
that  has  been  mentioned  in  connection  with  all  apparatus  that  is 
exposed  to  heat.  When  the  system  is  under  steam,  every  part 
through  which  the  steam  passes  assumes  a  temperature  equal  to,  or 
nearly  equal  to,  that  of  the  steam,  and  expands  with  it ;  and  when  the 
system  is  at  rest,  with  no  steam  passing  through  it,  or  even  when 
steam  remains  in  the  system,  but  with  engines  not  working,  and 
therefore  the  steam  is  at  rest,  cooling  takes  place,  the  pipes  following 
the  lower  temperature  and  contracting  with  it.  In  a  long  length  of 
pipe,  such  as  that  connecting  a  range  of  boilers  to  a  range  of  engines, 
as  in  an  electricity  generating  station,  and,  again,  long  pipes  connect- 
ing boilers  to  engines  at  a  distance,  the  expansion  and  contraction 
will  often  be  considerable,  especially  with  steam  at  high  pressures. 
The  difficulty  is  met  by  fixing  expansion  bends,  as  they  are  called, 
in  the  range  of  steam  pipes,  the  bend  moving,  altering  its  shape, 
taking  up  the  increased  length  due  to  the  expansion,  and  giving  back 
the  increased  length  it  received,  when  contraction  takes  place.  This 
is  the  more  modern  method  of  providing  for  expansion  and  contraction, 


28o     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

but  arrangements  on  the  lines  of  that  shown  in  Fig.  126,  known  as 
jointing  rings,  are  also  employed.     It  will  be  seen  that  the  ends  of 


FIG.  126. — "Wedgring"  Coupling  for   Steam   Pipes,  made   by  the   British   Steam 

Specialities  Co. 

the  pipes  are  held  by  the  couplings  shown,  the  expansion  and  con- 
traction being  taken  up  by  the  middle  portion  of  wedge  section, 
whose  shape  makes  provision  against  leakage  of  steam. 

Steam  Traps 

An  apparatus,  of  which  there  are  various  forms,  and  which  is  very 
necessary  in  all  steam  systems,  is  the  steam  trap,  to  collect  the  water 
formed  from  condensed  steam  in,  say,  a  long  range  of  pipes  or  where 
bends,  etc.,  occur.  As  explained,  it  is  a  very  serious  matter  for  water 
to  pass  into  an  engine  cylinder,  or  to  be  driven  violently  against  a 
dead  end. 

There  are  two  main  lines  upon  which  steam  traps  are  worked — by 
the  expansion  and  contraction  of  a  tube  or  rod  opening  and  closing  a 
valve,  allowing  the  water  to  pass  out  of  the  pipe  to  be  drained ;  and 
by  the  action  of  gravity,  the  weight  of  the  water  that  is  drained  from 
the  steam  pipe  closing  the  aperture  through  which  it  has  passed. 
The  trap  is  always,  or  should  be,  connected  to  the  lowest  part  of  the 
steam  pipes  to  be  drained,  and  it  should  contain,  or  discharge  into, 
a  vessel  from  which  the  condensed  water  gathered  by  it  can  be 
delivered  to  the  hot  well,  or  wherever  the  feed  water  for  the  boiler  is 
taken  from.  The  amount  of  condensed  water  collected  by  steam 
traps  on  a  large  service  of  steam  pipes  is  considerable  throughout  the 
day,  and  should,  in  many  cases,  effect  some  economy  in  steam  work- 
ing if  collected. 

In  all  cases  the  action  of  the  steam  trap  is,  or  should  be,  auto- 
matic. It  is  connected  to  the  pipe  by  drilling  a  hole,  or  the 


PLATE  ISA.     Rotor  of  Brush  and  Parsons'  Steam  Turbine. 


PLATE  18B.— Half  of  Stator  of  Brush  &  Parsons'  Turbine. 


PLATE   18c.— Brush  &  Parsons' 


Turbine  directly  connected  to  Alternator  and  its 
Exciter.  [To  face  p.  280. 


THE   STEAM   ENGINE 


281 


equivalent,  and  screwing  the  connecting  pipe  of  the  steam  trap 
into  it,  and  the  usual  arrangement  is,  the  steam  in  the  steam  pipe 
forces  out  the  water  that  has  been  condensed  in  front  of  it  through 
the  connecting  pipe,  into  the  trap  and  discharges  it,  and  then  closes 
the  valve  through  which  the  water  was  forced,  until  a  further 
quantity  is  collected.  Steam  traps  are  made  to  lift  the  condensed 
water  which  they  drain  off,  to  a  certain  height,  the  box  in  which 
the  trap  is  contained  being  made  to  withstand  higher  steam  pressures 
than  where  it  is  merely  to  act  as  a  water  holder,  and  the  pressure 
of  the  steam  inside  being  made  to  force  the  water  out. 

The  following  are  a  few  examples  of  different  forms  of  steam  traps. 

Brooke's  Steam  Trap.— In  this  apparatus,  which  is  shown  in 
Figs.  127  and  128,  the  expansion  and  contraction  of  a  metal  tube,  which 


FIG.  127. — Sectional  view  of  the  Brooke  Steam  Trap.  A  is  the  Steam  Pipe  to  be 
drained ;  E  is  the  Valve,  which  is  opened  and  closed  by  the  lever  D,  actuated  by 
the  expansion  and  contraction  of  A. 

is  open  to  the  steam  from  the  pipe  the  trap  is  intended  to  drain, 

actuates  a  valve,  which  automatically  discharges  the  water  that  has 

collected.     In  Fig.  127,  in  which 

the    whole    of    the    apparatus    is 

shown   in  section,  A   is   the  tube 

connected  to  the  steam  pipe,  into 

which  the  steam  enters,  and  it  is 

held  in  a  pair  of  rod  guides,  R  and 

HI,  the  upper  one  of  which  actuates 

the   lever   D,  which,   in   its   turn, 

opens  or  closes  the  valve  E  shown 

below. 

In  Fig.  128,  in  which  the  valve 
and  the  parts  connected  with  it  are 
shown  larger,  and  in  section,  the 
valve  with  its  vertical  rod  will  be 
noticed,  as  also  the  discharge  pipe 
on  the  left  and  the  connection 
between  the  steam  pipe  through 

which  the  water  enters,  and  the  space  leading  to  the  discharge,  which 
is  opened  when  the  valve  rises.     When  water  enters  the  tube  A, 


DISCHARGE 


FIG.  128. — Section  of  Discharge  End  of 
Brooke's  Steam  Trap.  Steam  enters 
by  the  Pipe  shown,  in  the  direction 
of  the  Arrow,  and  when  Water  also 
enters,  the  cooling  effect  contracting 
the  Steam  Pipe  actuates  the  Levers 
operating  the  Valve  shown,  opening 
it,  the  reverse  operation  closing  it. 


282     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

driven  into  it  by  the  steam  behind  it  in  the  steam  pipe,  the  presence 
of  the  water  lowers  the  temperature  of  the  tube,  causing  it  to  con- 
tract, and  to  compress  the  guide  rods  E,  El.  The  upper  guide  rod, 
as  explained,  then  works  the  lever  D,  depressing  the  valve  E,  opening 
a  passage  between  the  tube  A  and  the  discharge  opening,  the  water 
present  in  the  tube  then  being  driven  out.  Immediately  the  water 
has  been  driven  out,  a  certain  portion  of  the  steam  which  drove  it 
out  follows.  The  temperature  of  the  tube  A  then  being  raised,  it 
elongates,  carrying  with  it  the  guide  rods  E  and  El,  the  guide  E 
then  operating  the  valve  rod  of  the  valve  E  in  the  opposite  direction, 
closing  the  valve  and  shutting  the  discharge  pipe. 

In  the  arrangement  recommended  by  the  makers  of  the  Brooke 
steam  trap  for  draining  boiler  steam  pipes,  the  trap  is  connected  to 


FIG.  129. — Inside  view  of  "Sirius"  Steam  Trap.  The  semicircular  Tube  expands 
and  contracts  and  moves  the  Hod  to  and  fro.  closing  or  opening  the  Valve  on 
the  left. 

the  boiler  pipe  immediately  outside  of  the  stop  valve,  and  it  has  a 
cock  inserted  in  the  pipe  leading  to  the  trap,  by  which  the  trap  can 
be  shut  off  by  hand.  The  trap  is  made  for  pressures  up  to  200  Ibs. 
per  square  inch,  and  a  special  form  up  to  300  Ibs. 

Sirius  Steam  Trap — This  apparatus,  which  is  also  made  by 
Messrs.  Holden  &  Brooke,  is  shown  in  Fig.  129.  As  will  be  seen, 
the  principle  of  the  apparatus  is  very  much  the  same  as  that  of 
the  Brooke  trap,  but  the  expanding  tube  is  in  the  form  of  a  semi- 
circle. Also,  in  place  of  the  working  parts  of  the  trap  being  in  the 
open,  as  in  the  Brooke  trap,  they  are  all  enclosed  within  the  semi- 
cylindrical  case  shown.  The  case  with  the  inlet  and  outlet  pipes 
forms  a  complete  path  for  the  steam  when  the  trap  is  open.  When 
at  rest,  that  is  to  say  when  the  trap  is  cold,  when  no  steam  is  passing, 
the  trap  is  open,  and  therefore  when  steam  is  turned  on,  it  passes 


THE   STEAM   ENGINE 


283 


through  the  trap  case,  full  bore.  As  the  trap  warms  up,  the  semi- 
circular tube  expands  and  closes  the  entry  valve  on  the  left.  As  will 
be  seen,  the  expansion  and  contraction  of  the  tube  moves  the  rod, 
which  forms  the  diameter  of  the  semi-circle,  to  and  fro,  compressing 
and  elongating  the  spring  upon  the  rod.  The  semi-circular  tube  in 
this  case  does  not  receive  steam  on  the  inside.  It  responds  to  the 
heat  of  the  steam  in  the  vessel  in  which  it  is  enclosed.  When  water 
collects  in  the  trap,  the  cooling  effect  causes  the  semi-circular  tube  to 
contract  and  to  pull  back  the  sliding  rod  and  opening  the  valve, 
allowing  the  water  to  be  blown  out  by  the  steam,  after  which  the 
trap  is  again  warmed  up  and  tne  semi-circular  tube  expands  and 
closes  it. 

The  Lancaster  Steam  Trap. — The  Lancaster  steam  trap  is  a 
good  example  of  the  other  form  of  trap  mentioned — that  in  which 


FIG.  130.— Longitudinal  Section  of  Lancaster  Steam  Trap.     B  is  the  Box;  E  the 
Float ;  S  the  Axle  upon  which  the  Float  turns. 

a  float  is  employed  to  open  and  close  the  valve  discharging  the 
water.  Sections  of  the  valve  are  shown  in  Figs.  130  and  131. 
The  trap  consists  of  the  box  shown  in  Fig.  130,  in  which  the 
float  E  moves  up  and  down,  pivotted  upon  an  axle,  its  rising  and 
falling  being  controlled  by  gravity,  as  it  becomes  full  of  water 
or  discharges  it.  When  at  rest,  the  float  is  at  the  bottom  of  the 
box.  Connection  is  made  to  the  trap  through  the  pipe  which  forms 
the  hollow  steel  spindle  marked  S  in  Figs.  130  and  131,  upon 
which  the  float  E  moves.  When  the  trap  is  open  to  a  steam  pipe, 
any  water  that  may  be  present  is  driven  by  the  steam  through  the 
hollow  spindle  S  into  the  float  E,  gradually  causing  the  latter  to  fall. 
The  float  has  a  hole  at  the  bottom  of  the  end  removed  from  the 


284    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


spindle,  and  the  water  which  is  delivered  into  the  float  passes  through 
the  hole  F  into  the  body  of  the  box  forming  the  trap.     The  float  then 

becoming  buoyant,  rises  and  closes  the 
admission  valve.  The  steam  drives 
the  water  out  through  the  valve 
marked  N.  As  the  steam  left  in  the 
float  condenses,  water  from  the  box 
flows  into  it,  when  it  again  falls, 
opens  the  valve,  the  steam  that  enters 
driving  the  water  out,  and  so  on.  It 
is  claimed  that  as  long  as  the  trap 
is  connected  to  any  source  of  steam 
supply,  it  will  continue  to  work  to 
and  fro  in  the  manner  described, 
discharging  the  water  that  has  been 
brought  over  as  long  as  any  is  present. 
It  is  also  claimed  that  the  valve, 
having  a  twisting  motion,  automati- 

FIG.  131  -Transverse  Vertical  Sec-     cally  grinds  itself  steam-tight.      It  is 
tion  of  the  Lancaster  Steam  Trap        i    •       j      i        j.i_ij.u         J-J.IT 

shown  in  Fig.  130.    The  letters    claimed  also  that   the  adjustable  air 
refer  to  the  same  parts.  valve  N  at  the  top  of  the  float  over- 

comes    the    trouble    that    sometimes 

arises  from  the  re-evaporation  of  the  water  that  is  brought  over  with 
the  steam. 

The  Water-Seal  Steam  Trap.— The  water-seal  steam  trap  is 
claimed  to  be  a  steam  separator  and  a  steam  trap  as  well.  The 
apparatus  has  the  usual  steam  inlet  and  outlet,  and  is  arranged  to 
be  connected  in  the  steam  service  in  place  of  being  merely  tapped 
on  to  it.  The  steam  enters  on  one  side  of  a  short  casting  and  leaves 
by  the  other;  but  in  passing  through  a  spherical  portion  of  the 
casting  it  is  claimed  that  any  water  present  is  separated  from  the 
steam,  which  issues  dry  on  the  outlet  side,  the  water  being  carried 
down  into  a  sphere  at  the  bottom.  The  head  may  also  be  simply 
connected  to  a  steam  service,  instead  of  being  inserted  in  the  steam 
service.  The  inlet  and  outlet  of  the  head  are  of  the  same  diameter 
as  the  pipe  the  apparatus  is  to  drain,  but  the  spherical  portion  is 
usually  double  the  diameter.  On  the  steam  entering  the  head,  it  is 
claimed  that  the  water  on  the  lower  portion  of  the  entry  pipe  falls 
directly  into  the  globe  below,  to  which  the  head  is  connected.  The 
comparatively  dry  steam  is  made  to  follow  a  somewhat  circuitous 
course,  on  the  usual  lines  of  the  steam  separator,  in  its  passage  from 
the  inlet  to  the  outlet  ports,  and  during  this  passage  it  is  claimed 
that  the  remainder  of  the  water  is  separated. 

What  is  termed  a  sensitive  tube,  which  is  of  a  diameter  not  less 
than  that  of  the  steam  pipe  that  is  being  drained,  and  which  varies 


THE   STEAM   ENGINE  285 

in  length  from  8  to  16  inches,  is  fixed  to  the  lower  side  of  the  head,  and 
this  tube  performs  the  usual  office  of  opening  and  closing  the  water 
discharge  valve  by  its  expansion  and  contraction.  A  spherical  vessel 
is  attached  to  the  lower  portion  of  the  sensitive  tube,  and  inside  of 
the  sensitive  tube  is  a  smaller  discharge  tube  leading  to  the  discharge 
valve,  and  extending  nearly  to  the  bottom  of  the  lower  sphere.  The 
sphere  at  the  bottom  is  called  the  water-seal  chamber,  and  its  office  is 
to  cover  with  water  the  open  end  of  the  internal  discharge  tube,  so 
that  no  steam  can  pass  that  way.  There  are  two  rods  rising  from 
the  lower  globe  leading  to  levers,  which  operate  the  discharge  valve. 
As  the  sensitive  main  tube  rises  and  falls,  the  side  rods  open  and 
close  the  discharge,  valve  and  allow  the  water  that  has  collected  in 
the  lower  spherical  chamber  to  be  blown  out  by  the  steam,  the  valve 
being  closed  when  the  watec  has  been  blown  out,  and  reopened  later 
by  the  admission  of  water,  and  so  on. 


Steam  Traps  Operating  by  the  Expansion  of  a 
Volatile  Spirit 

There  is  a  line  of  steam  traps  made  by  the  Steam  Fittings  Co., 
in  which  the  usual  arrangement  of  an  expanding  and  contracting 
metal  rod  or  tube,  is  replaced  by  expansion  and  contraction  of  a 
volatile  spirit,  moving  a  diaphragm,  to  which  a  tube  is  attached,  whose 
motion  opens  and  closes  the  trap.  In  the  form  known  as  the  Midget, 
there  is  a  hollow  chamber  at  the  top  of  the  apparatus,  in  which  a 
flexible  diaphragm  is  stretched,  the  volatile  liquid  mentioned  being 
enclosed  in  the  space  above  the  flexible  diaphragm,  and  the  tube 
which  opens  and  closes  the  valve  being  attached  to  the  lower  part. 
Steam  enters  at  an  inlet  on  the  left,  and  when  the  central  tube  is 
raised,  it  passes  through  the  apparatus,  and  out  by  an  outlet  on  the 
right,  driving  any  water  that  may  be  present  before  it.  The  rising 
and  falling  of  the  flexible  diaphragm,  is  controlled  by  the  heat  of  the 
steam  when  present,  and  the  cooling  of  the  water  when  any  is  brought 
over.  When  the  spirit  is  condensed,  in  the  chamber  above  the 
diaphragm,  the  central  tube  rises,  and  allows  the  steam  and  water  to 
pass  through.  When  steam  passes  up  into  the  central  tube,  having 
driven  all  the  water  present  through  the  apparatus,  the  heating  effect 
of  the  steam  causes  the  volatile  spirit  to  evaporate,  the  pressure 
created  forcing  the  central  tube  down,  and  closing  the  trap,  this 
operation  going  on  continuously,  as  long  as  the  connection  is  made 
to  the  steam  pipe  to  be  drained,  and  there  is  water  to  be  carried 
away.  It  is  recommended  that  the  trap  should  be  fixed  as  close  as 
possible  to  the  apparatus  to  be  drained. 


286    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Reservoir  Steam  Trap 

The  reservoir  steam  trap  is  a  modification  of  the  Midget,  in- 
tended for  larger  work.  There  is  the  same  chamber,  with  an  inner 
chamber  formed  by  flexible  diaphragms,  controlling  the  valve  of  the 
apparatus,  but  it  is  below  the  entry  pipe  in  place  of  above,  as  in  the 
Midget.  The  rising  and  falling  of  the  valve  is  controlled  by 
the  evaporation  and  condensation  of  the  volatile  liquid  in  the  flexible 
chamber,  as  before,  but  the  water  that  passes  in  to  the  apparatus  is 
allowed  to  fill  the  chamber,  and  to  overflow  to  the  outlet  through  a 
tube  in  the  centre,  connecting  to  the  outlet  port.  The  reservoir  is  a 
copper  dome,  and  it  is  the  cooling  of  the  copper  dome  which  cools 
the  flexible  diaphragm  chamber,  by  conduction,  that  leads  to  the 
closing  of  the  pipe. 


The  Euston  Steam  Trap 

This  is  another  apparatus  made  by  the  Steam  Fittings  Co.,  in 
which  the  arrangement  of  the  valve  is  very  similar  to  that  of  the 
diaphragm  controlled  valves  described  above,  but  the  expanding  tube 
itself  forms  the  portion  of  the  valve  which  opens  and  closes,  and  is 
itself  operated  directly  by  the  heat  of  the  steam,  and  the  cooling 
effect  of  the  water.  The  tube  forming»the  valve,  and  which  responds 
to  the  change  of  temperature,  has  an  inner  tube,  whose  position 
can  be  regulated  by  a  screw  at  the  top  of  the  apparatus.  The 
water  that  is  brought  over  by  the  steam,  in  the  process  of  draining, 
is  forced  through  the  annular  space  between  the  two  tubes,  and  in 
its  passage  cools  the  outer  tube,  causing  it  to  contract,  thereby  rising 
and  opening  the  valve  for  the  passage  of  the  water  straight  through. 


The  Anderson   Trap 

This  is  an  apparatus  made  in  America,  in  which  the  opening  and 
closing  of  the  valve  is  controlled  by  the  rising  and  falling  of  a  ball, 
very  much  on  the  lines  of  the  ordinary  ball  cock  employed  for  house- 
hold water  supply,  the  expansion  and  contraction  of  the  ball  opening 
and  closing  the  valve,  in  place  of  the  rising  and  falling  of  the  water. 
One  feature  of  the  trap  is,  the  sediment  chamber  at  the  bottom,  into 
which  any  grit,  etc.,  that  comes  over  falls,  it  being  claimed  that  this 
prevents  the  valve  itself  being  choked  by  the  grit.  The  valve  of  the 
trap  is  sealed  with  3  or  4  inches  of  water,  and  it  is  claimed  that  this 
prevents  the  loss  of  steam. 


THE   STEAM   ENGINE  287 


Relief  Valves 

Eelief  valves  are  fitted  to  various  portions  of  the  steam  system, 
such  as  the  cylinder,  the  main  steam  pipe,  etc.,  and  they  are  made  in 
various  forms,  a  favourite  one  being  a  spring-loaded  valve,  which 
opens  when  the  tension  of  the  spring  is  overcome  by  the  pressure  of 
the  steam  in  the  space  the  valve  is  intended  to  protect. 

Valves  are  also  arranged  to  cut  off  boilers,  should  the  steam  main 
burst,  or  should  a  tube  in  one  of  the  boilers  burst.  The  arrangement 
consists  of  a  differential  valve,  kept  in  balance  so  long  as  the  system 
is  working  properly,  and  coming  into  operation,  and  closing  the 
valve,  should  the  steam  main  or  one  of  the  tubes  of  any  particular 
boiler  burst. 


CHAPTER  V 
THE  STEAM  TURBINE 

THE  steam  turbine  differs  from  the  reciprocating  engine,  in  the  very 
important  point  that  the  direction  of  motion  of  its  moving  parts  is 
never  reversed.  In  the  reciprocating  engine,  as  has  been  explained, 
the  piston,  which  receives  energy  from  the  steam  and  converts  it  into 
mechanical  energy,  moves  to  and  fro,  and  is  consequently  subject  to 
all  the  disadvantages  that  have  been  mentioned  in  connection  with 
to-and-fro  motion.  The  steam,  for  instance,  has  to  be  pushed  out  of 
the  cylinder,  after  it  has  done  its  work,  and  different  arrangements 
have  to  be  made  to  ensure  that  the  full  work  of  the  cylinder  of  steam 
is  obtained,  and  so  on.  In  the  turbine,  in  all  forms,  there  is  an  axle, 
upon  which  are  mounted  apparatus  designed  to  give  rotary  motion  to 
the  shaft  directly,  and  without  the  intervention  of  any  converting 
apparatus,  such  as  a  crank  shaft,  and  the  motion  so  obtained  is 
continuous,  so  long  as  the  steam  is  passing  through  the  apparatus, 
and  is  always  in  the  same  direction.  All  forms  of  turbine  have  a 
closed  vessel,  in  which  the  moving  axle  is  carried,  on  bearings,  just 
as  a  crank  shaft  is  carried,  the  enclosed  chamber  being  sufficiently 
large  to  accommodate  the  apparatus  that  is  to  receive  the  energy 
from  the  steam,  and  to  convert  it  into  rotary  motion. 


Classes  of  Steam  Turbines 

There  are  two  classes  of  steam  turbines,  known  respectively  as  the 
pressure  turbine  and  the  velocity  turbine,  the  latter  being  sometimes 
called  the  impulse  turbine.  Their  names  are  taken  from  the  fact 
that  the  one  receives  the  steam  at  the  full  pressure,  just  as  a  recipro- 
cating engine  does,  and  allows  it  to  expand  down  to  the  lowest 
pressure  obtainable  by  the  aid  of  a  good  condensing  apparatus ;  while 
the  other  receives  the  steam  at  the  lowest  pressure  that  can  be 
produced,  under  the  conditions,  whether  that  be  atmospheric  or 
condenser  pressure,  and  the  energy  of  the  steam  is  converted  into 

288 


PLATE  19A. — Parsons  Turbine,  made  by  Messrs.  Richardson  &  Westgarth,  showing 
Steam  and  Oil  connections,  Governor,  etc. 


PLATE  19s. — Richardson's,  Westgarth's,  and  Parsons'  Steam  Turbine  directly  con- 
nected to  two  Electricity  Generators,  as  viewed  from  the  Steam  end. 


PLATE  19c. — Richardson's,  Westgarth's,  and  Parsons'  Steam  Turbine  directly  con- 
nected to  a  Tube,  whose  Alternator  and  its  Exciter  are  seen  from  the  Generator 
end.  [To  face  p.  288. 


THE   STEAM  TURBINE  289 

mechanical  energy,  by  the  passage  of  the  steam  through  the  apparatus 
at  a  high  velocity.  The  two  forms  are  also  sometimes  called,  reaction 
(pressure),  and  action  (velocity)  turbines. 

There  is  an  intermediate  group  of  turbines,  in  which  the  steam  is 
expanded  down  to  the  exhaust  pressure  by  stages,  each  stage  forming 
a  velocity  turbine  in  itself,  but  the  different  stages  being  arranged 
with  regard  to  each  other,  very  much  as  the  different  cylinders  of  a 
compound  or  triple-expansion  reciprocating  engine  are,  and  the 
pressure  of  the  steam  being  gradually  lowered  at  each  stage. 

It  will  be  understood  from  what  has  been  stated  in  previous 
portions  of  this  book,  that  the  steam  possesses  energy  in  virtue  of  the 
heat  which  has  been  imparted  to  it  in  the  boiler,  part  of  it  being  the 
latent  heat  causing  it  to  change  its  physical  condition  from  water  to 
steam,  and  the  other  part  being  energy  imparted  to  it  after  its 
conversion  into  steam,  by  the  continuous  delivery  of  heat  to  it,  the 
continuous  generation  of  steam  in  the  boiler,  and  by  the  consequent 
increased  pressure  upon  the  steam  already  there.  Energy  may  be 
either  in  the  potential  or  kinetic  form.  By  potential  energy  is 
meant,  the  ability  to  perform  work,  if  certain  things  are  done  to 
the  object  possessing  the  potential  energy.  Thus,  a  rock  poised  at 
the  top  of  a  mountain  peak,  possesses  potential  energy  in  proportion 
to  its  weight  and  to  its  height  above  the  plain  below,  or  the  sea 
level,  if  it  is  able  to  reach  it ;  and  it  will  accomplish  the  work  repre- 
sented by  its  potential  energy  if  its  supports  are  removed,  say  by  its 
being  loosed  from  its  bed,  forced  over  the  precipice,  and  so  on. 
Similarly,  a  column  of  water  in  a  pipe,  extending  from  a  reservoir  at 
a  height  above  a  river  in  a  valley  below,  possesses  potential  energy, 
which  is  measured  by  the  weight  of  the  water  in  the  pipe,  and  the 
vertical  height  through  which  it  would  fall  in  passing  to  the  river,  or 
to  the  sea,  when  it  finally  reached  it. 

Immediately  potential  energy  is  released,  it  becomes  converted 
into  kinetic  energy.  Thus,  in  the  case  of  the  column  of  water,  when 
it  is  made  to  move  a  turbine  near  the  bottom  of  the  valley,  the 
kinetic  energy  possessed  by  the  moving  water  is  delivered  to  the 
turbine,  and  is  there  converted  into  mechanical  energy.  Similarly 
with  steam,  the  steam  present  in  the  boiler  possesses  potential 
energy,  in  proportion  to  its  pressure,  and  to  its  quantity.  Its 
potential  energy  is  converted  into  kinetic  energy  immediately  it 
commences  to  move,  whether  it  is  driving  the  piston  of  a  recipro- 
cating engine,  or  the  moving  member  of  a  turbine.  It  will  be 
remembered  also  that,  as  was  explained  in  Chapter  I.,  the  volume  of 
the  steam,  and  of  any  gas,  varies  inversely  with  the  pressure  to  which 
it  is  subject,  in  accordance  with  the  formula — 

pv  =  a  constant 

u 


29o    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

It  will  be  evident,  therefore,  that  given  a  certain  body  of  steam,  at  a 
certain  pressure,  if  it  is  allowed  to  expand  to  lower  pressures 
without  losing  or  receiving  heat  from  any  source,  adibiatically  as  it 
is  called,  the  larger  volume  of  the  steam  will  be  possessed  of  the  same 
amount  of  energy  as  the  smaller  volume,  and  will  deliver  its  energy 
to  any  apparatus  that  can  receive  it,  provided  that  arrangements  can 
be  made  to  utilize  the  energy  possessed  by  the  steam  at  the  lower 
pressure  without  loss.  And  this  is  what  is  done  in  the  velocity 
turbine.  The  steam  is  expanded  down  to  the  lowest  pressures 
obtainable  by  condensation,  in  the  latest  apparatus,  as  will  be 
explained,  about  1  Ib.  pressure  absolute,  and  the  energy  of  the 
enormously  increased  volume  of  the  steam  is  utilized  by  driving  it 
through  the  turbine  at  a  very  high  velocity.  In  the  table  given 
below,  taken  from  a  paper  read  by  Mr.  Konrad  Andersson  before  the 
Institution  of  Engineers  and  Shipbuilders  in  Scotland,  the  different 
velocities,  kinetic  energies,  and  horse-powers  are  given  for  steam  at 
different  initial  pressures,  when  opposed  to  different  counter  pressures. 


TABLE  XXIV. 

THE  VELOCITY  OP  OUTFLOW  AND  THE  WORKING  CAPACITY  OF  DRY 
SATURATED  STEAM. 


Counter-pressure  2-4  Ibs. 

Counter-pressure  0'93  Ibs. 

II 

Counter-pressure  1  atm. 

per  square  inch  absolute  corre- 
sponding to  25  inch  vacuum. 

per  square  inch  absolute  corre- 
sponding to  28  inch  vacuum. 

P.I 

& 

Kinetic 

H.P.  of 

Kinetic       H.P.  of 

Kinetic 

H.P.  of 

» 

i& 

Velocity 
ofoutflow 
of  steam. 

energy. 
Ft.-pounds 
per  second. 

550 
ft.  -pounds 
per  second. 

Velocity 
ofoutflow 
of  steam. 

energy. 
Ft.-pounds 
per  second. 

550 
ft.  -pounds 
per  second. 

Velocity     energy, 
of  outflow  Ft.-pounds 
of  steam.  P^  second. 

550 
ft.-pounds 
per  second. 

gi 

Feet  per 

Feet  per 

Feet  per  ' 

'•£  p 

"H£ 

second. 

Per  pound  of  steam 

second. 

Per  pound  of  steam 

second. 

Per  pound  of  steam 

per  hour. 

per  hour. 

per  hour. 

60 

2421 

25-29 

0-046 

3320 

47-57 

0-087 

3680        58-44 

0-106 

80 

2595 

29-06 

0-053 

3423 

50-56 

0-092 

3793 

62-08 

0-113 

100 

2717 

31-86 

0-058 

3520 

53-47 

0-097 

3871 

64-66 

0-118 

120 

2822 

34-37 

0-062 

3596 

55-80 

0-101 

3940 

66-99 

0-122 

140 

2913 

36-62 

0-066 

3661 

57-84 

0-105 

3999 

69-01 

0-125 

160 

2992 

38-63 

0-070 

3718 

59-65 

0-108 

4045 

70-61 

0-128 

180 

3058 

40-35 

0-073 

3764 

61-14 

0-111 

4091 

72-22 

0-131 

200 

3115 

41-87 

0-076 

3810 

62-64 

0-114 

4127 

73-50 

0-134 

220 

3166 

43-26 

0-079 

3852 

64-03 

0-116 

4159 

74-64 

0-136 

280 

3294 

46-83 

0-085 

3962 

67-74 

0-123 

4229 

77-18 

0-140 

It  will  be  understood  that  in  the  steam  turbine,  as  in  the  recip- 
rocating engine,  the  steam,  after  passing  through  the  turbine,  is  either 
exhausted  to  the  atmosphere,  or  into  a  condenser,  and  that  it  has  to 
force  its  way  out  against  the  pressure  of  the  atmosphere,  or  that  of 
the  condenser,  and  that  the  velocity  with  which  the  steam  passes 


THE   STEAM   TURBINE  291 

through  the  turbine,  is  reduced  by  the  counter  pressure.  Thus,  it 
will  be  seen  that  while  with  60  Ibs.  initial  pressure,  the  velocity  of 
outflow  of  the  steam  is  2421  feet  per  second  when  exhausting  to  the 
atmosphere,  it  becomes  3320  feet  per  second  with  a  vacuum  of  25 
inches,  and  3680  feet  per  second  with  a  vacuum  of  28  inches,  the 
velocity  of  steam  at  200  Ibs.  pressure  being  increased  from  3115  feet 
per  second  when  exhausting  to  the  atmosphere,  to  3810  feet  per 
second  with  25  inches  of  vacuum,  and  4127  per  second  with  28  inches 
of  vacuum.  A  very  striking  point  will  be  noted  here,  viz.  that  the 
velocity  of  the  steam  and  its  kinetic  energy  and  horse-power  is 
greater  with  60  Ibs.  initial  pressure  and  a  2 5 -inch  vacuum,  than  with 
200  Ibs.  initial  pressure  and  exhausting  to  the  atmosphere.  Also, 
that  with  60  Ibs.  initial  pressure  and  28-inch  vacuum,  the  velocity  of 
the  steam  and  the  horse-power  is  greater  than  with  140  Ibs.  initial 
pressure  and  the  25  inches  of  vacuum.  This  was  explained  fully  in 
the  first  chapter,  it  being  due  to  the  larger  quantity  of  heat  that  is 
set  free  at  the  lower  pressures. 

Difference  between  Pressure  and  Impulse 
Turbines 

It  will  probably  be  difficult  for  the  student  to  grasp  the  difference 
between  pressure  and  impulse  turbines,  or,  as  the  author  prefers 
to  call  them,  pressure  and  velocity  turbines,  because,  as  will  be  seen 
from  the  descriptions  given  further  on  in  the  book,  of  the  different 
forms  of  turbines,  the  construction  of  the  two  forms  is  almost 
identically  alike.  The  fundamental  difference  may  be  taken  to  be 
as  follows : — In  the  velocity  or  impulse  turbine,  there  are  one  or 
more  closed  chambers,  into  which  the  steam  that  is  to  drive  the 
turbine  wheel  is  expanded,  and  it  drives  the  wheel  purely  by  its 
velocity — by  the  speed  at  which  the  steam  passes  through  the  wheel. 
In  the  pressure  turbine  there  are  no  closed  chambers,  the  expansion 
of  the  steam  is  continuous  from  its  entry  to  its  exit.  It  expands  at 
each  of  the  guide  rings,  as  they  are  termed,  the  rings  of  blades 
separating  the  rings  of  blades  on  the  moving  member  of  the  turbine, 
and  it  also  expands  as  it  passes  through  the  blades  on  the  moving 
member  itself.  Further,  the  steam  can  pass,  not  only  through  the 
guide  blades,  but  round  them,  and  not  only  through  the  blades 
on  the  moving  member,  but  also  round  them,  in  the  small  space 
between  their  ends  and  the  enclosing  chamber. 

As  explained  above,  the  later  forms  of  impulse  turbines  are  really 
combinations  of  pressure  and  velocity  apparatus.  That  is  to  say, 
the  steam  is  expanded  from  the  initial  boiler  pressure  to  a  certain 
low  pressure  in  the  first  stage,  then  to  a  further  lower  pressure  in 
the  second  stage,  and  so  on. 


292    STEAM   BOILERS,  ENGINES,   AND   TURBINES 


Compounding  in   Pressure  Turbines 

The  different  sizes  of  rings  of  blades  in  the  pressure  turbine, 
correspond  to  the  different  sizes  of  cylinders  with  reciprocating 
engines,  the  steam  being  gradually  expanded  as  it  passes  through  the 
apparatus  from  the  entry  port  to  the  exhaust  port,  but  with  the 
great  advantage  over  the  reciprocating  engine,  that  the  expansion 
is  continuous  right  through  the  apparatus.  Thus  the  steam  entering 
at  the  smaller  end  of  the  enclosing  cylinder,  passes  through  the  first 
ring  of  blades,  then  through  a  ring  attached  to  the  casing,  then 
through  another  ring  on  the  axle,  through  a  second  ring  attached 
to  the  casing,  and  so  on.  In  passing  through  each  ring  of  blades, 
whether  attached  to  the  axle  or  to  the  casing,  the  steam  parts  with 
a  certain  portion  of  its  energy,  and  with  a  certain  portion  of  its  heat, 
its  pressure  becoming  lower  in  accordance  with  the  lowered  tempe- 
rature, as  explained  in  Chapter  I.  The  energy  it  parts  with  is 
delivered  to  the  blades,  and  a  certain  portion  of  it  acts  radially,  to 
give  motion  to  the  axle.  It  will  be  remembered  that  every  force 
can  be  resolved  into  two  forces  at  right  angles  to  each  other,  and  in 
this  case  the  force  acting  upon  each  inclined  blade,  is  resolved  into 
two  forces,  one  acting  longitudinally,  and  tending  to  force  the  whole 
of  the  rotor  against  its  end  bearings,  and  the  other  tending  to  cause 
the  rotor  to  revolve.  As  the  steam  passes  through  successive  rings 
of  blades,  its  pressure  and  temperature  being  lowered,  the  rings  of 
blades,  it  will  be  seen,  are  increased  in  diameter,  so  that  the  turning 
moment  given  to  the  axle  is  maintained  constant  throughout  the 
length  of  the  turbine;  this,  it  will  be  understood,  being  a  very 
important  point  in  connection  with  the  apparatus. 


Forms  of  Pressure  Turbine 

The  Parsons  Turbine. — The  earliest  form  of  pressure  turbine 
is  the  well-known  Parsons,  the  invention  of  Hon.  Charles  Parsons. 
Sections  of  this  turbine  are  shown  in  Figs.  132, 134  and  135,  and  also 
of  the  modifications  of  it  made  by  Messrs.  Willans  and  Eobinson.  The 
apparatus  consists,  as  will  be  seen,  of  a  long,  cylindrical  chamber, 
enclosing  the  axle  mentioned  on  a  previous  page,  the  axle  carrying 
a  number  of  blades,  slightly  inclined  to  the  radius.  The  blades  are 
held  within  enclosing  rings,  which  in  Messrs.  Willans'  apparatus  are 
of  the  form  shown  in  Fig.  133,  the  inner  end  of  the  blade  being  dove- 
tailed into  a  recess  provided  for  it  in  the  axle,  and  the  outer  end  held 
by  the  enclosing  ring.  The  rotor  and  stator  of  a  Brush-Parsons 
turbine  are  shown  in  Plates  ISA  and  18B,  and  complete  turbines  by 


THE   STEAM   TURBINE 


293 


the  Brush  Co.  and  Messrs  Bichardson's  Westgarth,  in  Plates  18c, 
and  19 A,  19s,  and  19c.  As  will  be  seen  from  the  figures,  a  number 
of  blades  are  assembled  together  to  form  a  complete  ring,  surrounding 
the  axle,  but  the  blades  being  slightly  inclined  to  the  radius  of  the 


FIG.  132. — Section  of  Parsons  Turbine,  showing  the  Equalizing  Pressure  Rings  at 

the  Steam  End. 

apparatus,  there  is  a  space  between  adjacent  blades.  Kings  of  blades 
are  placed  on  the  axle,  between  similar  rings  fixed  on  the  inside 
of  the  case,  which  in  the  Willans  form  are  built  up  in  exactly  the 
same  manner,  one  end  of  each  blade  being  dovetailed  into  the  case 


i 


SECTION    OF    BLMIiNd 


FIG.  133. — Willans'  arrangement  of  Rotor  and  Stator  Blades,  with  their  Containing 
Rings,  and  the  Joints  to  Shaft  and  Casing. 

in  a  slot  provided  for  it,  and  the  other  held  by  the  enclosing  ring.  In 
all  pressure  turbines  the  rings  of  blades  extend  from  the  axle  very 
nearly  to  the  inside  of  the  outer  case,  and  the  rings  of  blades  fixed 
to  the  cylinder  extend  almost  to  the  axle.  As  will  be  seen  from 


294    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

the  Plates  ISA  and  18B,  there  are  successive  rings  of  blades  increasing 
in  size,  and  the  diameter  of  the  enclosing  cylinder  also  increases  in 
size  from  one  end  to  the  other.  It  will  be  noticed  in  Plate  ISA, 
which  represents  the  rotor,  or  moving  member,  of  a  Brush-Parsons 
turbine,  that  the  rings  of  blades  extend  only  a  small  distance  radially 
outwards  from  the  axle  at  the  left-hand  end,  and  that  their  size 
increases  from  left  to  right.  The  rings  of  blades  fixed  to  the  inside 
of  the  cylinders  follow  the  same  increase.  The  sizes  of  the  blades, 
the  length  of  the  turbine,  the  number  of  the  rings  of  blades,  and  so 
on,  depend  upon  the  horse-power  that  is  to  be  developed  by  the 
turbine,  the  pressure  of  steam  that  it  is  to  work  with,  and  the 
quantity  of  steam  that  has  to  pass  through  it.  It  will  be  under- 
stood that  with  higher  pressures  of  steam,  the  numbers  of  sections 
of  rings  of  blades  will  be  more  than  with  lower  pressures,  and 
that  where  the  turbine  has  to  accommodate  a  large  quantity  of 
steam,  it  must  be  made  larger  in  diameter  than  where  it  has  only  to 
accommodate  a  smaller  quantity.  Thus,  with  a  comparatively  low 
pressure  of  steam,  the  turbine  would  be  shorter  longitudinally,  and 
larger  in  diameter  than  with  higher  pressure  steam,  for  a  given  horse- 
power. On  the  other  hand,  it  should  be  noted  that  the  work  done 
by  any  steam  turbine  is  so  largely  at  the  low-pressure  end  of  the 
steam  scale,  where  high  vacua  can  be  obtained,  that  there  is  not  a 
very  great  difference  between  the  sizes  of  turbines  for  high  and  low 
pressure  working. 

There  is  another  exceedingly  important  point  in  connection  with 
the  pressure  turbine,  and  that  is,  the  matter  of  the  end  thrust  just 
mentioned.  It  was  mentioned  above,  that  the  force  applied  to  the 
inclined  blades  was  resolved  into  two  forces,  at  right  angles  to  each 
other,  one  of  them  acting  in  the  direction  in  which  the  steam  is 
moving,  and  tending  to  force  the  shaft  longitudinally  against  its 
end  bearings.  In  some  of  the  early  machines,  it  was  found  that 
this  was  a  somewhat  serious  matter,  and  Mr.  Parsons  overcame  the 
difficulty  by  providing  a  dummy  axle,  forming  an  extension  of  the 
axle  proper,  beyond  what  would  be  the  end  bearing,  the  dummy  axle 
having  three  discs,  which  were  exposed  to  the  pressure  of  steam  at 
different  portions  of  the  rotating  apparatus.  In  an  earlier  form  of 
Parsons  turbine  also,  the  difficulty  was  overcome  by  making  the 
turbine  in  duplicate,  having  two  turbines  in  one  casing,  and  on  one 
axle,  and  admitting  the  steam  to  the  centre  between  the  two.  This 
is  only  used  for  small  sizes,  because  the  efficiency  of  the  steam  turbine 
increases  very  rapidly  with  the  size,  and  consequently  when  the  work 
was  divided  between  two  small  turbines,  in  place  of  one  large  one, 
the  consumption  of  steam  was  considerably  increased.  In  all  later 
forms  of  Parsons  turbine,  as  shown  in  Figs.  132  and  134,  rings  are 
fixed  on  the  rotor  axle  behind  the  steam  inlet,  which  are  exposed  to 


THE   STEAM   TURBINE 


295 


different  pressures  of  steam,  and  so  balance  the  pressure  due  to 
the  action  that  has  been  described.  In  Fig.  134,  which  is  a  section 
of  a  Willans-Parsons  turbine;  the  enclosing  case  is  shown  shaded, 
and  the  different  steam  spaces,  etc.,  are  marked  by  different  letters. 
Thus,  A',  A",  are  the  spaces  in  which  the  blades  of  the  rotor 
revolve,  and  in  which  the  stationary  rings  of  blades  are  also  fixed, 
the  spaces  being  larger  as  the  steam  inlet  is  receded  from.  J  is 
the  entry  port  for  the  steam,  C  is  a  disc  on  the  axle  immediately 
behind  the  entry  port,  and  exposed  to  the  full  steam  pressure  which 
enters  there,  and  D  is  another  disc  fixed  on  the  axle,  still  further 
behind  the  entry  port,  and  exposed  to  steam  acting  upon  the  inter- 
mediate blades  in  the  space  A',  connection  between  these  spaces  and 
the  disc  D  being  made  by  the  pipe  E.  The  pipe  H  which  is  seen 
below,  and  which  communicates  with  the  back  of  the  disc,  or  balance 


FIG.  134. — Section  of  Willans-Parsons  Steam  Turbine.  A  A,  A' A',  A"  A"  are  the 
several  Steam  Spaces ;  J  is  the  Steam-entry  port ;  C  and  D  are  the  Balance 
Discs  receiving  pressure  from  the  Steam  Spaces  by  the  passages  E  and  H,  H 
being  connected  to  the  Exhaust. 


piston  D,  is  in  connection  with  the  exhaust  B,  and  tends  to  keep  the 
apparatus  in  equilibrium. 

In  addition  to  the  steam  connections  mentioned  for  balancing  the 
end  thrust  of  the  rotor,  connections  are  arranged  to  admit  steam  of 
full  pressure  to  the  intermediate  sections  of  the  turbine  on  special 
occasions,  to  enable  it  to  pull  with  a  temporary  overload.  This  is 
the  equivalent,  in  turbine  work,  of  the  practice  that  is  sometimes 
employed,  of  admitting  high-pressure  steam  into  intermediate  or  low- 
pressure  cylinders  with  reciprocating  engines,  to  give  high  starting 
torque. 

The  Bearings  of  the  Parsons  Turbine. — The  bearings  of  tur- 
bines are  necessarily  of  very  great  importance,  since  the  rotors  and 
their  axles  revolve  at  very  high  speeds.  In  the  Parsons  turbine  the 


296    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

bearing  is  built  up  of  four  concentric  cylinders  having  spaces  between 
them,  which  are  filled  with  oil  under  pressure.  The  inner  cylinder 
forms  the  bearing  proper  and  consists  of  the  usual  gun-metal  sleeve, 
prevented  from  turning  by  a  loose-fitting  dowel,  and  the  object  of 
the  three  other  sleeves  is  to  enable  the  shaft  to  run  about  its  axis 
of  gravity  instead  of  its  geometric  axis,  the  journal  itself  running 
slightly  eccentric.  It  is  claimed  that  this  form  of  bearing  fulfils  the 
same  office  as  the  flexible  shaft  employed  in  the  De  Laval  turbine 
described  further  on.  The  four  cylinders  forming  the  bearing  are 
held  in  an  outer  cast-iron  sleeve,  and  in  all  forms  of  turbine  the 
bearings  are  very  long.  In  the  Parsons  turbine  there  is  an  oil  reser- 
voir under  the  bearing  at  the  steam  end,  as  shown  in  Fig.  135,  into 
which  the  oil  from  the  bearings  drains  after  it  has  done  its  work, 


FIG.  135. — Section  of  Parsons  Turbine,  with  Bearings,  Lubricating  Arrangement, 

and  Governor. 


and  from  which  it  is  pumped  to  a  chamber  above  the  bearings  at 
that  end,  from  which  it  runs  to  the  bearings  by  gravity,  the  necessary 
head  being  formed  in  the  chamber.  The  oil  pump  is  worked  by 
worm-wheel  gearing,  taking  motion  from  the  main  shaft. 

The  Governor  of  Parsons  Turbines. — In  Parsons  turbines  the 
steam  is  admitted  to  the  containing  cylinder  in  gusts,  the  quantity 
of  steam  admitted  to  the  turbine  at  each  gust  being  regulated  by  the 
time  the  admission  valve  is  open,  and  this  being  controlled  by  a 
relay  valve  worked  by  the  governor.  The  arrangement  of  the 
governor  is  shown  in  Figs.  135  and  136.  It  receives  motion  from 
worm  gearing  on  an  extension  of  the  main  shaft,  and  has  the  usual 
revolving  balls,  as  shown,  with  the  spiral  spring  opposing  their  out- 
ward motion.  The  vertical  rod  giving  motion  to  the  governor  also 
acts  as  a  fulcrum,  at  a  point  below  the  governor,  for  the  system  of 


THE   STEAM   TURBINE 


297 


levers  shown  in  Fig.  136.  In  the  figure  the  upper  portion  of  the  main 
steam  admission  valve  is  shown,  and  also  the  relay  valve  controlling 
it,  and  it  will  be  seen  that  the  relay  valve  is  worked  by  the  system 
of  levers  mentioned,  the  levers  receiving  motion  from  an  eccentric 
on  the  main  shaft,  the  levers,  the  eccentric  and  the  governor  together 
controlling  the  relay,  and  the  relay  controlling  the  time  the  main 
valve  is  open,  at  each  gust.  The  governor  controls  the  motion  by 
varying  the  plane  of  oscillation  of  the  relay  valve,  this  causing  the 
main  admission  valve  to  remain  open  a  longer  or  shorter  time.  It 
will  be  seen  that  this  arrangement  is  the  equivalent  of  the  admission 


FIG.  136. — Sectional  Drawing  of  Parsons  Steam-turbine  Governor.    A  is  the  Belay 

Valve. 

valve  of  a  reciprocating  engine  with  variable  cut-off,  but  with  the 
advantage  that  the  passage  of  steam  into  the  cylinder  is  always  in 
the  same  direction,  and  is  practically  continuous. 

For  governing  the  turbines  employed  for  driving  electricity 
generators,  Mr.  Parsons  employs  an  electrical  apparatus,  consisting 
of  a  solenoid  with  shunt  and  main  windings,  the  relay  operating  the 
main  admission  valve  being  controlled  by  the  pull  of  the  solenoid, 
and  this,  again,  being  controlled  by  the  work  the  generator  is  being 
called  upon  to  perform.  When  the  load  on  the  generator  increases, 
the  main  winding  of  the  electric  governor  receives  an  increased 
current,  the  shunt  winding  having  its  current  slightly  decreased,  and 
the  admission  valve  in  consequence  being  open  longer  at  each  gust, 


298    STEAM   BOILERS,  ENGINES,   AND   TURBINES 


THE   STEAM   TURBINE 


299 


while,  when  the  load  is  decreased,  the  main  winding  loses  a  portion 
of  its  pull  owing  to  the  decreased  current  passing  in  its  coils,  and 
the  shunt  winding  has  its  current  increased,  and  the  admission  valve 


FIG.  138.— Cross   Section  and  Plan  of  one  arrangement  of  Parsons  Turbines  for 

Steamship  Propellers. 

is  not  open  for  so  long.  Figs.  137  and  138  show  interesting  appli- 
cations of  Parsons  turbine.  Fig.  137  is  a  turbo  pump,  and  Fig. 
138  the  arrangement  of  turbines  for  driving  the  propellers  of 
steamships. 


300    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


The  Willans  Turbine  Governor 

In  the  "Willans  apparatus  the  governor  is  practically  the  equiva- 
lent of  the  throttle  governor  employed  in  the  Willans  central  valve 
engine.  It  is  a  very  powerful  centrifugal  governor  driven  by  worm 
.gearing  from  an  extension  of  the  main  turbine  shaft  at  the  steam 
end,  the  working  parts  moving  in  ball  bearings,  and  the  governor 
merely  opens  or  closes  the  admission  valve  more  or  less,  the  passage 
of  steam  into  the  turbine  being  continuous,  subject  to  the  amount 
the  valve  is  open. 

A  secondary  governor  is  arranged  in  the  Willans  apparatus  to 
automatically  close  the  throttle  valve  should  the  speed  of  the  turbine 
exceed  a  predetermined  limit.  It  should  be  mentioned  that  in 
several  forms  of  turbines,  automatic  arrangements  are  provided  for 
preventing  the  rotor  from  exceeding  its  normal  speed  by  more  than 
10  per  cent.  It  will  be  understood  that  at  the  high  speeds  at  which 
turbine  rotors  run,  centrifugal  force  increases  very  rapidly,  and  there- 
fore some  provision  of  this  kind  is  necessary  to  prevent  the  apparatus 
being  wrecked. 


Lubrication  of  the  Willans- Parsons  Turbine 

In  the  Willans-Parsons  turbine  there  is  an  oil  tank  under  the 
bearings  at  the  steam  end  as  in  the  Parsons  apparatus,  and  continu- 
ous circulation  of  oil  through  the  bearings  is  maintained  by  a  rotary 
pump  driven  direct  from  the  turbine  shaft.  It  is  claimed  that  the 
pump,  being  always  flooded,  ensures  a  complete  supply  of  oil  to  all 
the  bearings  immediately  the  turbine  commences  to  move.  A  hand 
pump  is  also  fitted  in  the  Willans  apparatus  by  which  the  bearings 
can  be  flushed  before  starting  the  turbine.  It  should  be  mentioned 
that  the  question  of  lubrication  of  the  bearings  before  starting  is  an 
exceedingly  important  one,  and  that  great  care  must  be  exercised  to 
see  that  the  bearings  are  thoroughly  well  lubricated  before  the  turbine 
is  started. 

The  Brush = Parsons  Turbine 

The  Brush  Electrical  Engineering  Company,  who  have  been 
engaged  in  electrical  work  in  the  construction  of  electricity  generators, 
and  prime  movers  for  them,  since  the  advent  of  the  Brush  machine 
in  the  very  early  days  of  the  electric  light,  have  taken  up  the  manu- 
facture of  steam  turbines  on  the  lines  of  the  Parsons  apparatus.  The 
construction  is  very  similar  to  that  of  the  Willans-Parsons  and  that 


THE   STEAM   TURBINE  301 

made  by  Mr.  Parsons'  own  company.  The  rotating  axle  is  made  of 
forged  steel,  machined  all  over,  and  the  blades  are  securely  held  in 
grooves  turned  in  the  axle.  In  large-sized  turbines  the  axle  consists 
of  a  cast  steel  tube.  The  blades  are  of  hard  drawn  metal,  and  those 
near  the  steam  entry  port,  which  are  exposed  to  high-pressure  steam, 
are  specially  designed  to  stand  high  temperatures. 

The  control  of  steam  to  the  turbine  is  very  similar  to  that  in  the 
Parsons.  There  is  an  ordinary  centrifugal  governor,  driven  by  worm 
and  wheel  from  the  main  shaft,  controlling  a  small  steam  relay 
actuating  an  equilibrium  valve,  which  is  opened  for  a  certain  period 
with  each  oscillation  of  the  governor.  A  separate  emergency  governor 
is  provided,  which  shuts  off  the  steam  when  the  speed  exceeds  a 
certain  limit. 

The  bearings  are  on  the  same  lines  as  those  of  Parsons.  For  sizes 
up  to  500  K.W.  (670  H.P.)  the  bearing  proper  is  of  solid  gun-metal, 
with  a  series  of  concentric  tubes  fitting  loosely  round  it  with  oil  in 
between.  Above  500  K.W.  the  bearings  are  of  brass  lined  with  white 
metal.  The  Brush-Parsons  turbine  is  shown  in  Plates  ISA,  18B, 
and  18c. 

The  De  Laval  Turbine 

The  De  Laval  turbine  was  the  earliest  of  the  velocity  turbines. 
It  consists  of  a  disc  held  upon  an  axle  and  having  buckets  fixed  all 
round  the  edge  of  the  axle,  the  whole  being  enclosed  in  a  case.  One 
side  of  the  case  is  connected  to  a  condenser,  with  the  aid  of  which  the 
highest  possible  vacuum  is  obtained,  and  the  steam  is  brought  to 
the  other  side  of  the  turbine  case  and  is  expanded  right  down  to  the 
vacuum  pressure,  and  is  allowed  to  pass  through  the  buckets  on  the 
periphery  of  the  disc  at  the  high  velocity  due  to  the  low  pressure, 
the  large  volume  of  steam  passing  from  the  other  side  of  the  disc  to 
the  condenser  and  turning  the  disc  in  the  process.  The  steam  is 
expanded  down  to  the  pressures  named  in  the  nozzles  shown  in 
section  in  Fig.  139.  It  will  be  noticed  that  the  nozzle  gradually 
expands  from  the  throat  just  beyond  its  connection  to  the  steam 
pipe  to  the  edge  of  the  disc.  The  pressure  in  the  steam  pipe  behind 
the  nozzle  being  200  Ibs.  per  square  inch,  the  pressure  at  the  throat 
of  the  nozzle  is  110  Ibs.  per  square  inch,  this  being  the  economical 
pressure  at  that  point. 

The  volume  of  the  steam  is  now  increased  from  2'8  to  3*5  cubic 
feet  per  pound,  and  its  velocity  in  the  throat  is  1500  feet  per  second. 
At  the  widest  part  of  the  nozzle,  where  the  pressure  corresponds 
to  28  inches  of  vacuum,  the  volume  of  the  steam  has  increased  to 
256*8  cubic  feet  per  pound,  and  its  velocity  to  4127  feet  per  second. 
The  nozzle  continuously  diverges  from  the  throat,  and  the  steam  is 


302    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

presented  to  the  wide  surface  of  the  disc  shown.  Several  nozzles  are 
fixed  to  each  turbine,  and  it  is  arranged  to  use  one,  two,  or  more 
according  to  the  power  the  turbine  is  to  deliver.  Further,  as  seen  in 
Fig.  139,  which  is  a  complete  section  of  the  nozzle  and  steam  entry 
valve,  the  admission  of  steam  to  the  nozzle  can  be  controlled  very 
much  as  the  admission  of  steam  is  controlled  to  an  ordinary  steam 
engine. 

The  velocity  of  the  turbine  wheel  for  high  efficiency  should  be 
34  per  cent,  of  the  velocity  of  steam  impinging  upon  the  turbine  disc, 
the  absolute  velocity  of  the  steam  when  leaving  the  buckets  would 
then  be  34  per  cent,  of  the  initial  velocity  of  the  steam.  It  is  found 
in  practice,  however,  impossible  to  run  the  turbine  discs  at  the  high 
speeds  demanded  by  this  law.  With  steam  entering  the  turbine  case 
at  a  velocity  of  4000  feet  per  second,  the  speed  of  the  turbine  wheel 
should  be  1880  feet  per  second  for  higher  economy.  At  present 


FIG.  139.— Section  of  Nozzle  of  De  Laval  Turbine. 

however,  the  peripheral  speed  of  the  turbine  wheel  does  not  exceed 
1380  feet  per  second.  The  difference  between  the  speed  of  highest 
efficiency  and  the  highest  practical  speed  makes  a  difference  in 
theoretical  steam  consumption  of  0*7  Ib.  per  horse-power.  That  is  to 
say,  with  the  turbine  wheel  running  at  the  speed  of  highest  efficiency, 
the  theoretical  steam  consumption  per  horse-power  per  hour  should 
be  9'1  Ibs.,  and  with  the  wheel  revolving  at  1380  feet  per  second  the 
theoretical  steam  consumption  should  be  9 '8  Ibs.  per  horse-power 
hour.  These  figures  are  not  obtained  in  practice.  The  theoretical 
steam  consumptions,  it  will  be  understood,  are  never  obtained  in 
actual  practice,  but  the  above  shows  the  difference  made  by  the  speed 
of  the  turbine.  Another  point  in  connection  with  the  high  speed  of 
the  turbine  is  the  matter  of  balancing.  No  matter  how  carefully  a 
high-speed  turbine  wheel  may  be  turned  and  balanced,  it  is  practically 
impossible,  so  it  is  found  by  the  makers,  to  bring  the  centre  of  gravity 
of  the  wheel  exactly  in  the  geometrical  centre  round  which  the  wheel 


THE   STEAM  TURBINE  303 

revolves,  and  with  the  ordinary  arrangement  of  shaft,  the  vibrations 
so  caused,  increasing  as  they  would  with  the  speed,  would  render  it 
impossible  to  maintain  any  bearings,  no  matter  what  lubrication  was 
employed,  with  the  high  speeds  at  which  the  wheel  runs.  There  is, 
however,  a  peculiar  feature  about  the  apparatus  which  has  enabled 
the  difficulty  to  be  overcome.  In  place  of,  as  in  almost  every  other 
kind  of  revolving  apparatus,  arranging  for  the  shaft  upon  which  the 
turbine  wheel  revolves  to  maintain  its  axial  line  rigid,  the  shaft  is 
made  flexible,  by  being  smaller  than  would  be  usual  under  similar 
conditions  for  other  work.  The  vibrations  caused  by  the  out-of- 
balance  of  the  turbine  wheel  occur  with  the  flexible  shaft,  and  increase 
with  the  number  of  revolutions  of  the  wheel,  but  at  a  certain  speed, 
known  as  the  critical  speed  of  the  wheel,  the  vibrations  suddenly 
disappear  and  the  shaft  runs  smoothly  in  its  bearings.  The  inventors 
and  makers  of  the  apparatus  have  termed  the  phenomenon  "the 
settling  of  the  wheel,"  and  they  explain  by  the  fact  that  at  the 
critical  speed  the  wheel  takes  a  new  centre  of  rotation  very  near 
to  the  centre  of  gravity,  the  shaft  springing  out  and  allowing  it.  It 
is  stated  that  the  phenomenon  has  not  been  investigated  scientifically, 
but  the  probable  explanation  is  that,  at  the  critical  .  speed,  the 
number  of  vibrations  and  the  number  of  revolutions  are  equal.  The 
following  formula  is  given  for  calculating  the  critical  speed  :  — 


Where  P  is  the  force  required  to  bend  the  shaft  a  certain  distance, 
Q  is  the  weight  of  the  turbine  wheel,  and  C  is  a  constant.  It  is 
stated  that  the  critical  speed  is  from  one-sixth  to  one-eighth  of  the 
standard  number  of  revolutions  of  the  wheel. 

It  will  be  understood  that  the  speed  of  the  turbine  wheel  being 
so  very  great,  the  power  developed  in  each  individual  revolution  is 
very  small,  and  therefore  the  size  of  the  shaft  is  enabled  to  be  small, 
and  the  flexibility  mentioned  is  thereby  provided  for.  The  shaft  of  a 
300  H.P.  turbine  wheel  is  only  l-fa  inches,  and  that  of  a  150  H.P. 
wheel  1  inch. 


Government  of  the  De  Laval  Turbine 

The  De  Laval  turbine  is  governed  by  a  sensitive  centrifugal 
governor,  mounted  horizontally  on  the  end  of  the  gear  wheel  shaft, 
with  the  usual  revolving  balls,  opposed  by  a  spring,  and  controlling 
the  valve  through  which  admission  is  obtained  by  the  steam  to  the 
steam  chest,  from  which  the  nozzles  that  have  been  described  obtained 
their  supply.  The  governor  is  practically  a  throttle  governor,  and  is 


FIG.  140.— Governor  of  De  Laval  Turbine.  B  B  are  the  usual  weights,  which  move 
outwards,  compressing  the  Spring  shown,  and  pushing  the  Rod  G  over  to  close 
the  Steam  Valve  on  the  right. 


FIG.  141. — Section  of  Steam  Valve  controlled  by  the  Governor. 


PLATE  2lA.— De  Laval  Turbine  directly  connected  to  a  60  Horse-power  De  Laval 
Turbine  Pump,  used  for  Boiler  Feed. 


PLATE  2lB. — De  Laval  Turbine  directly  connected  to  a  De  Laval  15  Horse-power 

Turbine  Pump.  [To  face  p.  304. 


THE   STEAM   TURBINE 


305 


stated  to  maintain  the  speed  between  full  load  and  no  load  within 
from  2  to  3  per  cent.  It  is  shown  in  Fig.  140,  and  the  valve  it 
controls  in  Fig.  141. 


Transmitting  the  Power  of  the  De  Laval  Turbine 

Wheel 

It  will  easily  be  understood  that  at  the  very  high  speeds  at  which 
the  De  Laval  turbine  wheels  run,  which  are  given  in  the  table  below, 
that  it  is  practically  impossible  to  gear  them  directly  to  any  machine 
to  which  the  power  is  to  be  applied,  and  therefore  the  turbine  wheel 
is  always  sent  out  with  the  gearing  wheels  attached,  as  shown  in 
Fig.  142,  reducing  the  speeds  down  to  any  figure  that  maybe  desired. 
The  shaft  of  the  spur  wheel  of  the  gearing  may  carry  a  pulley  for 
driving  any  apparatus  by  belt  or  ropes,  or  it  may  be  geared,  as  shown 
in  Fig.  143,  directly  to  a  dynamo,  pump,  or  other  apparatus.  In 
Fig.  142  and  Plate  20A  the  turbine  is  shown  transmitting  power  to 
two  axles,  the  pinion  on  the  shaft  of  the  turbine  engaging  with  a 
spur  wheel  on  each  side  of  it. 

Plates  20B,  2lA,  2lB,  and  22A  show  applications  of  the  De  Laval 
turbine  to  the  driving  of  various  apparatus,  and  Fig.  144  shows  the 
various  parts  of  the  turbine. 


TABLE   XXV. 
SPEEDS  OP  THE  TURBINE  WHEELS. 


Size  of  turbine. 

Middle  diameter  of 
wheel. 

Revolutions  per  minute. 

5  HP. 

Mm.    Inches. 
100          4 

30,000 

15 

150        6 

24,000 

30 

225        8g 

20,000 

60 
100 

300      11^ 
500      19? 

16,400 
13,000 

300 

760      30 

10,600 

Peripheral  speed. 
Feet  per  second. 


515 

617 

774 

846 

1115 

1378 


A  very  interesting  series  of  tests  of  a  50  H.P.  De  Laval  steam 
pump  is  given  in  Table  XXVI.,  and  further  tests  of  De  Laval  Turbines 
with  different  loads  is  given  in  Table  XXVII. 

x 


3o6    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


THE    STEAM    TURBINE 


307 


FIG.  143. — De  Laval  Turbine  directly  connected  to  a  Turbine  Pump. 


FIG.  144.— Parts  of  the  De  Laval  Turbine.     B  is  the  Turbine  Wheel ;  I  the  Nozzle  ; 
A  the  Shaft ;  M  Gear  Wheel,  etc. 


308     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


TABLE  XXVI. 

EESULTS  OF  TESTS  WITH  DE  LAVAL  STEAM  TURBINE  PUMPS. 


Type  of  turbine 
pump. 

Revolu- 
tions per 
minute. 

Height  of 
suction  in 
feet. 

Height  of 
delivery 
in  feet. 

Quantity 
of  water 
delivered 
per  second. 

Water 
H.P. 

Brake 
H.P. 

Efficiency. 

Gallons. 

50  H.P.  duplex) 

pump  coupled  > 
in  parallel        j 

1500 

16-4 

16-4 

63-5 

37-87 

50-3 

0-753 

50  H.P.  duplex^ 

| 

pump  coupled 

! 

in        parallel. 

i 

Constructed 

1500 

16-4 

29-53 

46-3 

38-66 

48-0 

0-805 

for  larger  head 

of  water  than 

the  previous    ) 

50  H.P.  duplex 

pump  coupled 

2200 

19-7 

137-8 

123-0 

35-22 

50-3 

0-700 

in  series 

20  H.P.  duplex 

pump  coupled 

2315 

9-84 

85-3 

82-5 

14-27 

20-0 

0-713 

in  series 

TABLE  XXVII. 
BESULTS  OF  TESTS  WITH  DE  LAVAL  STEAM  TURBINES  AT  DIFFERENT  LOADS. 


* 

Pressure  of 

Pounds  of 

Turbine  machine. 

admission 
eteam. 

Vacuum 
inches  of 

Number 
of  nozzles 

Electrical 

TT   p 

steam  per 
electrical 

Remarks. 

'Pounds  per 
square  inch. 

mercury. 

open. 

H.P.  per 

hour. 

1 

50  H.P.  turbine  f 

113-8 

26-3 

6 

49-4 

24-6 

Work  for  con- 

dynamo.    The] 

113-8 

26-3 

5 

40-2 

25-2 

densing  in- 

test   made    in) 

93-9 

26-9 

4 

25-0 

27-9 

cluded. 

April,  1895        ( 

74-0 

27-5 

3 

12-7 

32-5 

100  H.P.  turbinef 

103-7 

25-8 

5 

92-7 

22-6 

Work  for  con- 

dynamo.    Thel 
test    made    inj 

103-8 
107-4 

26-4 
26-8 

3 

2 

55-6 
35-0 

22-7 
24-7 

densing  not 
included. 

June,  1897        ( 

106-7 

27-9 

2 

15-5 

27-8    ' 

THE  STEAM   TURBINE 


309 


TABLE   XXVII.  (continued). 


Turbine  machine. 

!  Pressure  of 
admission 
steam. 
Pounds  per 
square  inch. 

V  acuum 
inches  of 
mercury. 

Number 
of  nozzles 
open. 

Brake 
H.P. 

Pounds 
steam  p« 
brake  H. 
per  hou 

113-8 

26-4 

7 

163-0 

17-6 

150  H.P.  turbine 

116-9 

25-9 

6 

138-4 

18-2 

motor.         The 

113-8 

26-2 

5 

114-5 

17-9 

trial    made    in\ 

114-3 

26-5 

4 

88-3 

18-7 

Nov.  ,  1897 

I     112-4 

27-0 

3 

64-1 

19-0 

( 

116-2 

25-7 

2 

37'5 

22-3 

/ 

192-7 

27-3 

7 

303-6 

14-1 

300  H.P.  turbine  \ 
motor.         The 
test    made    in 
Deo.,  1899 

;    196-3 

i     196-3 
196-3 
;     190-6 
i     196-3 

27-6 
27-6 
27-6 
27-8 
28-1 

6 
5 
4 
3 

2 

255-5 
216-9 
172-6 
121-6 
74-2 

14-7 
14-4 
14-5 
14-9 
17-2 

213-3 

28-5 

1 

31-5 

21-6 

126-6 

26-98 

8 

337-45 

15-68 

300  H.P.  turbine 
motor.         The 
test     made    in 
June,  1900 

126-4 
i     125-0 
125-0 
125-0 
125-0 

26-99 
27-24 
27-62 
27-91 
28-16 

7 
6 
4 
3 

2 

293-7 
249-1 
162-7 
118-9 
73-5 

15-76 
15-92 
16-25 
16-70 
18-00 

!     125-0 

28-25 

1 

30-4 

21-77 

Remarks. 


Work  for  con- 
densing not 
included. 


Work  for  con- 
densing not 
included. 


Work  for  con- 
densing not 
included. 


Messrs.  Greenwood  &  Batley,  the  makers  of  the  De  Laval  tur- 
bine, recommend  the  ejector  condenser  for  use  with  their  apparatus, 
and  when  a  central  condenser  is  employed,  they  require  that  a 
vacuum  governor  shall  be  inserted  in  the  pipe  between  the  condenser 
and  the  turbine. 


The  Curtis  Turbine 

The  Curtis  turbine  is  a  modification  of  the  De  Laval,  arranged 
primarily  to  reduce  the  speed  of  the  revolving  wheel.  It  consists 
really  of  several  turbines,  usually  fixed  vertically,  one  above  the 
other,  each  turbine  consisting  of  moving  and  stationary  discs,  both 
carrying  buckets  on  their  peripheries  similar  in  form  to  those  of  the 
De  Laval  apparatus.  The  separate  stages,  as  they  are  called,  are 
divided  by  diaphragms,  through  which  the  steam  passes,  each  dia- 
phragm having  a  set  of  steam  nozzles,  somewhat  similar  .to  those  of  the 


310    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


De  Laval,  the  steam  nozzles  of  the  upper  stage,  where  the  steam  first 
enters  the  apparatus,  being  directly  in  connection  with  the  steam 
chest.  The  steam  passes  through  the  buckets  of  the  upper  disc  in 
each  stage,  and  then  through  the  buckets  of  the  stationary  disc. 
From  Fig.  145,  which  shows  two  stages,  it  will  be  seen  that  the 
steam  passes  from  the  nozzles  directly  into  the  moving  buckets, 
without  changing  its  curves  appreciably,  on  entering  ;  that  it  passes 
out  as  the  buckets  move  on,  also  with  little  appreciable  change  of 
course  ;  that  on  reaching  the  stationary  buckets  it  enters  them  also 
'without  changing  its  course,  but  that  its  course  is  reversed  in  passing 


illnn  n 


NOZZLE 

MOVING   BLADES 
STATIONARY  BLADES 
MOVING   BLADES 


I     I 


NOZZLE 
DIAPHRAGM 


MOVING  BLADES 
STATIONARY     BLADES 

MOVING  BLADES  )])l)DDI))DD])i])DD^])D]))I)])])D)I)])])M 

1     1    \     I      1      I 

FIG.  145. — Section  of  Part  of  Curtis  Turbine,  showing  two  Stages.  The  Nozzles 
are  shown  inclined,  the  stationary  buckets  dark  and  the  moving  blades 
light. 

through  the  stationary  buckets,  and  that  it  is  then  presented  to  the 
moving  buckets  of  the  next  disc  in  the  proper  direction  to  enter  them 
without  change  of  course. 

The  steam  is  brought  comparatively  to  rest  after  passing  through 
the  last  moving  bucket  of  each  stage  before  passing  on  to  the  next 
stage.  The  diaphragms  between  the  stages  are  steam-tight,  except 
where  the  nozzles  open  into  them  as  shown. 

The  early  forms  of  Curtis  turbine  were  made  with  horizontal 
shafts,  but  all  the  later  ones  have  been  made  vertical ;  and  the  usual 
arrangement  now  is :  The  turbine  is  mounted  above  the  condenser,  a 


THE   STEAM   TURBINE  311 

vertical  shaft  passing  through  the  whole  apparatus,  on  to  a  footstep 
bearing,  consisting  of  two  bearing  blocks,  one  of  which  rotates  with 
the  shaft,  the  other  being  fixed  to  the  foundation.  Water  is  forced 
up  through  a  hole  in  the  stationary  part  of  the  bearing  out  between 
the  two  surfaces  in  contact  in  a  thin  film,  and  it  afterwards  passes 
upwards  to  lubricate  a  guide  bearing,  and  thence  passes  into  the 
turbine  base,  from  which  it  is  removed  with  the  condensed  steam. 
The  water  for  the  bearing  is  supplied  by  a  small  pressure  pump  and 
hydraulic  accumulator,  the  power  used  being  stated  to  be  1  H.P.  for  a 
1000  H.P.  set,  and  2  for  a  2000  H.P.  set.  The  upper  bearings  are 
lubricated  by  a  small  oil  pump  worked  from  the  shaft  of  the  water 
pressure  pump,  the  oil  being  returned  to  an  oil  tank  from  the  bear- 
ings, and  used  over  and  over  again.  It  will  be  evident  that  the 
upper  bearings  being  merely  guides,  so  long  as  the  apparatus  is  in 
balance,  lubrication  of  them  does  not  present  so  difficult  a  problem 
as  that  of  horizontal  shafts. 


Governing  the  Curtis  Turbine 

The  governor  of  the  Curtis  turbine  is  practically  a  throttle 
governor  of  the  usual  centrifugal  type,  with  moving  balls,  etc.  An 
emergency  governor  is  also  provided  for  cutting  off  the  steam  if  the 
turbine  exceeds  a  certain  figure. 

The  governor  is  connected  to  an  electrical  controller,  which  opens 
or  closes  a  series  of  electro  magnets,  operating  pilot  valves,  which 
open  or  close  the  main  steam  valves,  the  latter  being  of  the  balance 
type. 

Where  the  Curtis  turbine  is  employed  for  driving  dynamo 
machines,  it  is  usual  to  fix  the  dynamo  above  the  turbine,  as  shown 
in  Fig.  146,  and,  as  explained,  the  condenser  below,  the  vertical  shaft 
being  practically  continuous  throughout  the  apparatus. 

The  makers  of  the  Curtis  turbine  recommend  surface  condensers, 
and  with  sets  of  500  K.W.  (670  H.P.)  and  upwards,  that  the  con- 
denser shall  occupy  the  space  below  the  turbine,  the  pumps  being 
worked  from  the  turbine  shaft. 

Several  claims  are  made  for  the  Curtis  turbine,  one  of  which,  in 
particular,  is  the  fact  that  very  much  smaller  floor  space  is  required. 
As  against  this,  makers  of  horizontal  turbines  and  of  reciprocating 
engines  point  out  that  the  foundations  must  be  stronger,  and  usually, 
therefore,  carried  down  much  deeper  than  is  necessary  with  horizontal 
apparatus,  either  reciprocating  or  turbine. 


312     STEAM   BOILERS,   ENGINES,   AND   TURBINES 


0  0   ( 
0  0  0   C 


I?IG.  146. — Sectional  elevation  of  Curtis  Turbine,  with  Dynamo  above  and  Condenser 

below. 


PLATE  22A.  -De  Laval  Turbine  directly  connected  to  a  Fan. 


PLATE  22B. — A  Zoelly  Turbine,  made  by  Escher,  Wyss,  &  Co. 

[To  face  p.  312. 


THE   STEAM   TURBINE  313 


Test  of  a  1500  Kilowatt  Curtis  Turbo  Generator 

The  following  test  of  a  1500  K.W.  Curtis  turbo  generator,  made 
for  the  Corporation  of  London  Electric  Supply  Company,  will 
probably  be  interesting.  The  turbine^  were  of  the  four-stage  type, 
the  condenser  occupying  the  space  below  the  turbine,  and  the 
dynamos  being  fixed  above,  the  overall  height  from  the  condenser 
base  to  the  governor  above  the  dynamo  being  19  feet  6  inches,  and 
the  floor  space  15  feet  X  14  feet.  A  portion  of  the  apparatus  was 
fixed  below  the  engine-room  floor,  so  that  the  height  from  the 
engine-room  floor  to  the  top  of  the  governor  was  14  feet  6  inches. 
The  condenser  was  of  the  surface  type,  and  had  a  cooling  surface  of 
4000  square  feet,  the  air  pumps  being  of  the  three-throw  type,  with 
15-inch  cylinders  by  8-inch  stroke,  driven  by  a  15  K.W.  electric 
motor.  The  centrifugal  pump  was  driven  by  a  30  K.W.  motor. 
The  turbine  footstep  bearing  was  provided  with  water  from  the  well 
at  a  pressure  of  400  Ibs.  per  square  inch  by  three-row  bucket  pumps, 
driven  by  2  K.W.  motors.  The  steam  pressure  was  150  Ibs.  per 
square  inch,  the  steam  was  superheated  60°  F,  and  the  vacuum  was 
29  inches,  with  a  barometer  at  30*15  inches.  The  consumption  of  steam 
was  17£  Ibs.  per  K.W.  hour,  at  full  load,  and  20  Ibs.  per  K.W.  hour 
at  a  third  of  full  load ;  or  12 '44  Ibs.  per  horse-power  hour  at  full  load, 
15  Ibs.  per  horse-power  hour  at  one-third  load. 

The  steam  taken  by  the  auxiliaries  brought  the  total  consumption 
up  to  13*32  Ibs.  per  horse-power  hour  at  full  load.  It  will  be  seen 
that  the  Curtis  turbine,  though  it  is  strictly  a  velocity  turbine,  is  also 
partly  a  pressure  turbine,  inasmuch  as  the  expansion  of  the  steam  is 
performed  within  the  turbine  itself.  Figs.  147  and  148  show  the 
apparatus  tested. 

Westinghouse  Turbine 

The  Westinghouse  Company,  as  the  author  understands,  make  two 
forms  of  turbines,  one  on  the  lines  of  the  Parsons  turbine,  and  as 
made  by  the  other  makers  that  have  been  described,  and  the  other 
apparatus  which  is  a  combination  of  the  Curtis  and  Parsons  turbine. 
The  latter  form  is  fixed  at  the  Lots  Eoad  generating  station  on  the 
Metropolitan  District  Eailway  in  London,  and  is  arranged  for  fur- 
nishing 5500  K.W.  (7330  H.P.)  each,  driving  three-phase  generators. 

The  turbines  are  arranged  with  their  shafts  horizontal,  and  the 
steam  is  delivered  to  the  middle  of  the  apparatus.  The  Curtis 
portion  of  the  turbine  receives  the  steam  first,  and  the  Parsons 
apparatus  afterwards.  There  is  only  one  stage  of  the  impulse 
turbine  on  each  side  of  the  entry  port,  the  steam  entering  at  160  Ibs. 


3H    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


FIG.  147. — Elevation  of  a  Part  of  an  Electricity  Generating  Station,  with  Curtis 
Turbine,  Dynamo,  Condenser,  and  Accessories. 


Stairs  to  Air  Pur 

FIG.  148.— Plan  of  the  Portion  of  Electricity  Generating  Station  shown  in  Fig.  147. 


THE   STEAM   TURBINE 


pressure,  and  being  expanded  down  to  60  Ibs.  before  entering  the 
pressure  turbine.  The  impulse  turbines  consist  of  nozzles  for 
expanding  the  steam,  then  rows  of  guide  buckets  and  revolving 
buckets,  the  steam  then  passing  on  to  a  receiver,  for  the  remaining 
portion  of  the  turbine,  in  which  it  is  expanded  down  to  condenser 
pressure.  There  are  in  the  pressure  portion  of  the  turbines  three 
rows  of  turbine  wheels,  with  brass  vanes,  and  with  the  usual 
stationary  vanes  between  on  each  side.  The  arrangement  enables 
the  whole  apparatus  to  be  made  very  much  shorter  for  the  power  that 
is  employed,  than  is  usual  in  the  ordinary  form  of  Parsons,  or 
impulse  turbines. 

The  difference  between  working  with  the  condenser  and  without 
at  Lots  Road  is,  the  author  understands,  60  per  cent. 


The  Rateau  Turbine 

The  Eateau  turbine,  made  by  Messrs.  Eraser  &  Chalmers,  is  also 
a  velocity  or  impulse  turbine,  but  like   the  Curtis,  it   also  has  a 


FIG.  149. — Section  of  one  Form  of  Bateau  Turbine.     Steam  enters  on  the  left  and  is 
gradually  expanded  down,  as  it  passes  through  the  different  stages. 


number  of  moving,  and  of  fixed  elements,  the  expansion  of  the 
steam  being  performed  partly  in  the  turbine  itself.  The  apparatus 
consists  of  a  containing  cylinder,  usually  fixed  horizontally,  and 
somewhat  similar  to  those  that  have  been  described  in  connection 
with  the  Parsons  turbine.  The  moving  and  stationary  portions  of 
the  apparatus  are  also  constructed  something  on  the  lines  of  the 
Willans.  The  vanes  are  mounted  on  the  peripheries  of  steel  discs, 
the  moving  discs  being  fixed  directly  on!  the  axle,  and  the  stationary 
discs  being  fixed  on  the  inside  of  the  containing  cylinder,  and  closely 


316    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

embracing  the  shaft,  which  passes  through  them  in  collars  of  anti- 
friction metal.  The  fixed  discs  are  called  diaphragms,  and  their 
office  is  said  to  be  the  distribution  of  the  steam  to  the  moving  discs. 
The  steam  passes  first  through  the  vanes  of  the  diaphragms,  and  is 
directed  by  them  on  to  the  vanes  on  the  moving  discs,  so  that  the 
direction  of  the  steam  is  not  changed  on  meeting  them,  the  steam 
then  passing  from  the  moving  disc  to  the  vanes  of  the  next  diaphragm, 
where  its  course  is  directed  so  as  to  meet  the  vanes  of  the  next 
moving  disc  in  the  proper  direction,  and  so  on.  There  is  a  distance 
of  about  -fa  inch  between  the  moving  and  fixed  portions  of  the 
Eateau  turbine,  this  construction  having  been  adopted  to  reduce 
chances  of  dangerous  friction,  and  the  possibility  of  breakdown.  It 
is  claimed  that  there  is  no  longitudinal  thrust  on  the  moving  part, 
and  therefore  there  is  no  necessity  for  apparatus  to  balance  that 
thrust.  The  Eateau  turbine  is  sometimes  made  in  two  portions,  as 
shown  in  Fig.  149,  the  high-pressure  steam  entering  at  one  end, 
as  shown,  passing  through  the  first  portion  of  the  apparatus,  which, 
it  will  be  seen,  is  divided,  very  much  as  in  the  early  Parsons  turbine, 
and  afterwards  passing  through  the  low-pressure  apparatus,  as  shown 
in  the  figure. 

The  governor  is  of  the  usual  centrifugal  type,  controlling   the 
admission  valve  to  the  steam  chest. 


The  A.  E.G.  Steam  Turbine 

The  A. E.G.  steam  turbine  is  an  impulse  or  velocity  turbine,  with 
two  stages  only,  and  its  axle  runs  horizontally.  Its  construction  is 
shown  in  Fig.  150,  in  which  the  two  stages  and  the  revolving  wheels 
can  be  seen.  The  steam  enters  the  turbine  by  the  main  throttle 
valve,  passing  through  a  steam  separator  into  the  steam  chest,  then 
through  nozzles  of  a  form  similar  to  those  that  have  been  described 
on  to  the  first  stage  of  the  moving  buckets.  After  passing  through 
the  first  lot  of  the  moving  buckets,  it  passes  through  a  ring  of  fixed 
buckets,  its  direction  being  arranged  in  passing  through  them,  so  as 
to  enter  a  second  set  of  moving  buckets  at  the  proper  angle.  After 
passing  through  the  second  moving  wheel  it  enters  an  intermediate 
receiver,  passing  from  there  through  a  second  set  of  nozzles,  and 
through  the  moving  buckets,  and  guide  buckets  of  the  second  stage. 

When  running  non-condensing,  it  is  arranged  that  only  part  of 
the  steam  enters  the  second  stage  of  the  turbine,  the  remainder  being 
exhausted  directly  to  the  atmosphere. 

The  turbine  wheels  are  constructed  of  specially  selected  steel, 
and  the  buckets  of  a  special  bronze.  The  buckets  are  dovetailed 
into  the  turbine  wheels,  and  the  turbine  casing  is  made  of  cast  iron. 


THE  STEAM   TURBINE 


The  steam  is  expanded  to  about  atmospheric  pressure  in  the  first 
stage,  and  down  to  condenser  pressure  in  the  second  stage. 


FIG.  150. — Section  of  one  Form  of  the  A.E.G.  Steam  Turbine. 


The  Zoelly  Turbine 

The  Zoelly  turbine  is  also  an  impulse  or  velocity  turbine,  but 
with  a  number  of  stages,  the  inventors  claiming  that  better  results 
are  obtainable  by  dividing  up  the  work  into  a  number  of  stages,  as 
it  enables  the  velocity  of  the  steam  to  be  reduced,  and  thereby 
reduces  the  wear  upon  the  turbine  blades.  The  Zoelly  turbine  for 
large  sizes  is  made  in  two  portions,  as  shown  in  Fig.  151  with  a 
bearing  between  the  two,  the  high-pressure  portion  being  at  one  end 
and  the  low  pressure  at  the  other.  The  whole  apparatus  is  arranged 
horizontally,  the  turbine  wheels  rotating  in  vertical  planes.  Each 
half  of  the  apparatus  is  also  divided  longitudinally  into  two,  the 
upper  half  lifting  off,  so  that  the  wheels  can  be  got  at  for  inspection. 
There  are  the  usual  guide  wheels,  dividing  the  turbine  up  into 
chambers,  as  in  the  Eateau  and  others  that  have  been  described. 
The  guide  wheels  consist  of  discs  fixed  to  the  inside  of  the  containing 
cylinders,  and  with  vanes  fixed  near  their  peripheries,  for  the  guidance 
of  the  steam  in  the  usual  manner.  The  moving  wheels  or  runners 
consist  of  wrought-steel  discs,  accurately  turned  and  balanced  and 


318     STEAM    BOILERS,   ENGINES,   AND   TURBINES 


THE   STEAM    TURBINE 


machined  all  over,  provided  with  a  groove  in  their  peripheries,  in 
which  their  blades  are  fixed.     They  are  shown  in  Figs.  152,  153. 

As  in  the  other  forms  of  impulse  turbines,  the  runners  revolve  in 
the  chambers  formed  by  the  guide  blades,  the  latter  directing  the 
steam  on  to  the  vanes  of  the  runners  in  the  proper  direction. 


J3U 


FIG.  152. — Banner  of  Zoelly  Steam  Turbine,  in  Plan 
Elevation. 


FIG.  153. — Stationary  Blade 
of  Zoelly  Turbine. 


The  clearance  between  the  rotating  and  stationary  parts  of  the 
apparatus,  in  the  larger  sizes,  is  J  inch. 

The  bearings,  as  will  be  seen  in  Plate  22B,  are  supported  by  the 
bed  plate,  and  are  claimed  not  to  be  subject  to  heating  from  the 
steam  casing.  As  in  other  forms  of  impulse  turbines,  the  axle  is 
supported  throughout  its  length  by  the  collars  in  the  centres  of  the 
guide-rings. 


o  * 

^••\<   iKDRMl*^/^ 


320    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

The  governor,  a  section  of  which  is  shown  in  Fig.  154,  consists  of 
an  oil  relay,  working  with  a  pressure  of  oil  of  90  Ibs.  per  square  inch, 
which  works  the  main  steam  valve,  and  which  is  itself  controlled  by 
a  smaller  valve,  shown  to  the  left  in  the  figure,  worked  by  the  governor. 
In  the  drawing  the  governor  is  seen  on  the  extreme  left,  with  the 
usual  balls  arranged  to  rotate  in  the  usual  manner,  and  giving  motion 
as  they  rise  and  fall  to  one  end  of  a  lever,  to  which  are  attached 
rods,  moving  the  small  controlling  valve  of  the  oil  system,  and  the 
oil  relay  and  main  steam  valve.  As  the  governors  rise  and  fall,  oil 


FIG.  154. — The  Governor  of  the  Zoelly  Turbine.  The  rising  and  falling  of  the 
Governor  Spindle  moves  the  Arm  of  the  Lever  shown,  up  and  down,  its  other 
Arm  working  the  Oil  Belay,  which  in  its  turn  moves  the  Valve  below.  A 
Transverse  Section  of  the  Oil  Kelay  is  shown  in  the  middle  of  the  figure. 

is  admitted  through  the  small  controlling  valve,  to  the  oil  relay, 
lifting  it,  and  with  it  opening  the  steam  valve,  or  closing  it, 
according  to  the  load  that  is  on  the  turbine.  The  oil,  after  passing 
through  the  relay,  returns  to  the  oil  tank,  through  the  small  control 
valve,  and  is  pumped  up  again. 

The  steam  passes  continuously  into  the  turbine,  the  steam  valve 
being  opened  to  a  certain  definite  distance,  corresponding  to  each  load 
on  the  turbine. 

There  is  an  emergency  governor,  which  shuts  off  the  steam  if  the 
speed  exceeds  10  per  cent,  above  the  normal. 


THE   STEAM   TURBINE  321 

There  is. also  an  overload  valve  arranged  to  obtain  additional 
power  for  temporary  purposes,  and  to  obtain  full  power  when  the 
turbine  is  working  non-condensing,  by  the  admission  of  full- pressure 
steam  to  the  later  stages  of  the  turbine. 


The  Hamilton  Holzwarth  Steam  Turbine 

This  apparatus,  which  is  made  by  the  Hooven  Owens,  Eentschler 
Co.,  of  Hamilton,  Ohio,  U.S.A.,  has  certain  special  features  that  are 
of  interest.  For  apparatus  of  1000  H.P.  and  upwards  the  turbine  is 
divided  into  two  portions,  for  high-  and  low-pressure  steam.  For 
apparatus  below  1000  H.P.  the  turbine  is  in  one  casing.  The  turbine 
casings,  pedestals  for  bearings,  and  for  the  electricity  generator,  when 
the  turbine  is  employed  for  driving  it,  are  fixed  upon  a  bed  plate  of 
the  box  pattern,  very  much  on  the  lines  of  the  Zoelly,  and  on  the 
lines  adopted  in  the  case  of  Lancashire  mill  engines,  and  other  large 
engines  of  that  type.  All  steam,  oil  and  water  piping,  including 
the  steam  inlet  and  bye-pass  valves,  are  carried  in  the  bed  plate 
below  the  level  of  the  turbine.  A  steam  separator  is  fixed  in  the 
bed  plate,  and  the  steam  passes  through  it  to  the  main  inlet  valve, 
from  which  it  passes  through  a  regulating  valve  to  the  high-pressure 
turbine.  The  turbine  is  on  the  lines  of  the  Parsons,  the  stationary 
wheels  being  held  on  the  inside  of  the  cylinders,  as  usual,  and 
extending  very  nearly  to  the  axle.  The  stationary  discs  are  fixed  in 
grooves  in  the  turbine  casing,  the  vanes  being  riveted  to  the  discs, 
and  being  of  drop  forge  steel,  fixed  in  grooves,  on  the  outside  peri- 
pheries of  the  discs.  The  running  wheels  are  built  up,  it  is  claimed, 
of  great  strength.  Cast-steel  hubs  are  fixed  on  the  axle,  steel  discs 
being  riveted  to  both  sides  of  the  hubs,  forming  circumferential  ring 
spaces  in  which  vanes  are  held  by  means  of  rivets,  the  outer  edge  of 
the  vanes  being  held  by  a  thin  steel  band. 

The  bearings  are  of  the  ordinary  split  pattern,  lubricated  by  oil 
under  pressure.  The  governor  is  of  a  special  form,  driven  directly 
by  worm  gearing  from  the  turbine  shaft,  and  it  actuates  a  double- 
seated  poppet  valve. 

The  governor  shuts  off  the  supply  of  steam,  if  the  angular  velocity 
reaches  a  point  2J  per  cent,  above  the  normal,  and  opens  it  more  or 
less  in  proportion  to  the  steam  required  for  the  work  in  front  of  the 
turbine. 

Lubrication  is  very  similar  to  that  in  the  Parsons  turbine.  A 
portion  of  the  bed  plate  is  formed  into  an  oil  tank,  and  an  oil  pump, 
driven  by  worm  gearing  from  the  turbine  shaft,  forces  the  oil  through 
the  bearings,  from  which  it  flows  back  to  the  tank,  a  valve  enabling 
the  pressure  of  oil  to  be  regulated. 

y 


322     STEAM   ENGINES,   BOILERS,   AND    TURBINES 

The  Forms  of   Buckets  and   Blades  of  Steam 

Turbines 

There  is  not  space  within  the  limits  of  this  book  to  give  full 
particulars  for  the  mathematical  calculation  of  the  forms,  sizes  of 
buckets  and  vanes  of  steam  turbines,  but  the  following  may  be  of 
service.  The  design  of  both  buckets  and  vanes  must  follow  certain 
lines.  One  is,  the  steam — and  the  same  rule  applies  more  forcibly  with 
water — must  impinge  on  the  bucket  or  vane  without  shock.  If  steam 
or  water  impinges  upon  a  surface  in  such  a  manner  as  to  be  thrown 
back,  or  broken  up  by  the  impact,  a  large  portion  of  the  work  it  is 
capable  of  doing  is  lost,  and  therefore  all  forms  of  buckets  or  vanes 
are  designed  so  that  the  water  or  the  steam  glides  into  them,  and 
passes  through  them,  with  as  little  friction  or  shock  as  possible, 
passing  out  of  them  in  the  same  manner,  but  with  as  small  an  amount 
of  energy  remaining,  that  is  to  say,  with  as  low  a  velocity  as  possible. 
This  applies,  of  course,  where  the  whole  of  the  energy  is  to  be  taken 
out  of  a  moving  stream  of  water  or  steam  by  one  ring  of  buckets  or 
vanes.  Where  the  steam  is  to  pass  through  a  succession  of  rings  or 
buckets  or  vanes,  each  ring  is  designed  to  take  out  its  own  particular 
portion  of  energy,  passing  the  steam  on  to  the  next  ring,  and  so  on. 

In  order  that  the  steam  or  water  may  follow  the  above  rules,  it 
should  enter  the  bucket  or  vane  tangentially,  and  leave  it  tangentially. 
Put  in  another  way,  the  direction  in  which  the  steam  enters  the 
bucket  or  vane  should  be  a  tangent  to»fche  curve  formed  by  the 
bucket  or  vane  at  the  point  where  the  steam  or  water  enters,  and 
the  direction  in  which  it  leaves  the  bucket  or  vane  should  be  a 
tangent  to  the  curve  of  the  bucket  or  vane  at  the  point  of  exit.  It 
must  not  be  forgotten,  of  course,  that  the}  bucket  and  the  vane  are 
both  moving,  and  that  the  line  of  the  curve  of  either  is  not  the  same 
when  the  steam  or  water  enters,  as  it  is  when  it  leaves.  These  points 
have  all  to  be  calculated,  or  set  off  by  graphic  methods. 

Another  point  in  connection  with  both  water  and  steam  is,  as 
mentioned  above,  the  velocity  or  the  energy  possessed  by  the  steam 
on  leaving  should  be  as  small  as  possible.  On  the  other  hand,  a 
certain  amount  of  energy  is  necessary  to  be  left  in  the  case  of  water, 
or  it  cannot  get  away  from  the  turbine  wheel ;  and  in  the  case  of 
steam,  a  certain  amount  of  energy  remains,  because  the  whole  of 
the  energy  cannot  be  taken  out  of  the  steam  by  any  known  method. 

Turbines  Working  with   Exhaust  Steam 

To  Professor  Eateau  is  due  the  credit  of  the  idea  of  working 
steam  turbines  by  the  exhaust  steam  from  engines  that  are  working 


THE  STEAM   TURBINE 


323 


intermittently,  such  as  the  winding  engines  at  collieries,  the  rail-mill 
engines  at  iron  works,  and  others ;  but  other  makers  of  turbines  have 
taken  up  the  idea,  and  there  is  no  reason,  so  far  as  the  author  is 
aware,  that  any  one  of  the  turbines  on  the  market  should  not  be 
applied  to  the  same  use,  provided  that  proper  arrangements  are 


Wiltr  I»M  &* 


FIG.  155. — One  form  of  Professor  Bateau's  apparatus  for  storing  the  heat  from  the 
Exhaust  Steam  of  irregularly  running  Engines,  for  use  in  Turbines.  The  Cast- 
iron  Traps,  shown  on  the  right,  are  held  inside  the  Vertical  Cylinder,  shown  on 
the  left. 

made.  The  Zoelly  turbine,  for  instance,  has  been  adopted  for  work 
of  the  kind  at  Eombach  near  Metz,  where  two  900  B.H.P.  turbines 
are  running  electricity  generators,  fed  with  exhaust  steam. 

The  reason  of  the  adaptability  of  turbines  for  working  with 
exhaust  steam,  is  the  fact  pointed  out  several  times  already,  that 
the  largest  portion  of  their  work  is  obtained  on  the  lower  part  of 


324    STEAM   ENGINES,   BOILERS,   AND   TURBINES 

the  steam  scale.  As  the  exhaust  steam  from  intermittently  working 
engines  is  irregular,  it  is  necessary  that  some  arrangement  shall  be 
provided  for  storing  the  steam,  or  the  heat  present  in  the  steam, 
during  the  times  of  large  exhaust,  so  that  the  surplus  at  those  times 
can  be  utilized  to  make  up  for  the  deficiency  during  the  times  when 
the  engines  are  standing.  The  turbines  can,  of  course,  be  employed 
for  working  with  exhaust  steam  from  regularly  running  engines,  such 
as  fan  engines,  the  blast  engines  of  blast  furnaces,  and  others ;  and  it 
is  a  question,  in  those  cases,  whether  more  is  gained  by  employing 
the  exhaust  steam  in  a  turbine,  or  sending  it  to  the  condenser  directly. 
Where  condensation  is  not  practicable  from  one  of  the  causes  that 
have  been  mentioned,  there  can  be  hardly  any  doubt  of  the  economy 
of  utilizing  the  exhaust  in  a  low-pressure  turbine. 

Professor  Eateau  has  worked  out  several  methods  of  storing  the 
heat  of  the  surplus  steam,  some  of  which  are  shown  in  Figs.  155  and 


FIG.  156. — Another  form  of  Rateau's  Heat-storage  Apparatus.  The  Steam  passes 
into  the  Water  surrounding  the  Elliptical  Pipes  shown,  through  holes  in  the 
Pipes,  causing  circulation  of  the  Water,  etc. 

156.  The  apparatus  are  really  heat  accumulators,  and  the  arrange- 
ments are  all  designed  to  store  the  whole  of  the  surplus  heat  coming 
over  in  the  exhaust  steam,  and  to  give  it  up  readily  when  the  engines, 
from  which  the  exhaust  is  taken,  are  standing.  One  form  consists  of 
a  number  of  cast-iron  trays,  with  water  in  them,  standing  in  a  vertical 
cylindrical  chamber.  This  arrangement  is  shown  in  section  in  Fig. 
155.  The  exhaust  steam  enters  at  the  bottom  of  the  apparatus,  and 
the  steam  that  is  required  for  the  turbine  that  is  working  from  it 
leaves  at  the  top.  Water  is  supplied  to  the  apparatus,  when  required, 
by  the  pipe  shown,  and  can  be  run  off  as  required. 

Another   arrangement  consists  of  a  cylindrical   shell,   such  as 
that  of  an  old  Lancashire  boiler,  usually  fixed  horizontally,  partially 


THE  STEAM  TURBINE  325 

filled  with  old  iron  rails.  The  exhaust  steam  from  the  engines 
enters  the  old  boiler,  as  in  the  other  case,  passing  out  at  the 
opposite  end  to  the  turbine,  and  any  steam  that  is  not  required  for 
the  turbine  gives  up  its  heat  to  the  iron  rails.  In  another  method,  one 
or  more  cylinders  are  arranged  horizontally,  about  two -thirds  full  of 
water,  and  have  elliptical-shaped  pipes,  as  shown  in  Tig.  156,  arranged 
inside  of  them,  very  much  on  the  lines  of  the  flues  of  a  Lancashire 
boiler,  the  pipes  being  pierced  with  a  large  number  of  holes.  The 
exhaust  steam  passes  into  these  pipes,  and  from  them  to  the  turbine, 
a  quantity  of  the  steam,  however,  passing  out  through  the  holes  in 
the  pipes,  and  causing  a  violent  circulation  of  water  within  what  is 
practically  a  steam  boiler. 

In  either  arrangement  the  heat  is  stored  in  the  water  or  the  iron, 
the  temperature  of  the  water  and  the  iron  being  raised  in  consequence, 
and  the  water  being  prevented  from  evaporating  by  the  steam  pressure 
within  the  accumulator,  so  long  as  there  is  plenty  of  steam  to  feed 
the  turbine.  When  the  supply  of  steam  from  the  exhaust  of  the 
engines  fails,  the  pressure  of  the  steam  within  the  accumulator  being 
lowered,  the  temperature  of  evaporation  of  the  water  is  also  lowered, 
as  explained  in  Chapter  L,  steam  comes  away,  passes  to  the  turbine, 
and  provides  the  necessary  supply  to  keep  it  running. 

It  will  be  evident  that  it  is  not  possible  to  obtain  the  full  value 
of  the  whole  of  the  exhaust  steam,  since  some  must  be  kept  for 
storage,  but  a  large  percentage  is  obtained,  and  results  in  considerable 
economy.  The  apparatus  has  been  applied  to  several  collieries  and 
iron  works  on  the  Continent,  and  to  a  few  collieries  in  the  United 
Kingdom.  The  impulse  turbine  of  Professor  Eateau  is  claimed  to  be 
better  for  this  purpose  than  the  pressure  turbine  of  the  Parsons  type, 
but  it  appears  to  the  author  that,  providing  the  turbine  is  constructed 
for  the  lower  pressures,  either  apparatus  should  answer  equally  well. 

An  adjunct  of  the  arrangement  that  has  been  adopted  in  some 
cases,  is  a  connection  to  the  boiler  furnishing  steam  for  the  engines, 
the  steam  from  the  boiler  being  automatically  turned  on  to  the 
turbine,  should  the  quantity  of  steam  available  in  the  accumulator 
fall  below  a  certain  figure.  The  arrangement  includes  a  thermostat 
working  a  differential  valve,  the  valve  remaining  closed  so  long  as 
the  pressure  on  the  turbine  side  of  it  reaches  a  certain  figure,  viz. 
that  sufficient  to  keep  the  turbine  going.  Should  the  pressure  on 
the  turbine  side  of  the  differential  valve  be  lowered  to  such  a  point 
that  the  turbine  would  tend  to  slow,  the  differential  valve  comes  into 
operation,  and  opens  the  connection  directly  to  the  boiler,  the  turbine 
then  working  directly  with  live  steam  until  the  accumulator  has 
sufficient  storage  to  keep  it  going.  It  is  a  question  whether  it 
is  more  economical  to  work  the  arrangement  in  this  manner.  By 
the  aid  of  the  supply  from  the  boiler,  the  heat  accumulator  can  be 


326    STEAM   BOILERS,  ENGINES,  AND  TURBINES 


THE  STEAM  TURBINE  327 

of  smaller  size  than  when  it  is  to  provide  the  whole  of  the  steam 
required,  and  the  whole  of  the  exhaust  steam  can  be  used.  It  is 
again  a  question  of  the  balance  sheet,  as  in  all  these  cases.  There 
is  the  cost  of  the  additional  steam  taken  from  the  boiler,  the  interest 
on  the  additional  apparatus  required,  the  cost  of  looking  after  the 
apparatus,  as  against  the  cost  of  the  additional  size  of  the  accumulator. 
It  appears  to  the  author,  also,  that  Mr.  Druitt  Halpin's  system 
of  thermal  storage  should  be  applicable  in  this  case.  Mr.  Halpin's 
apparatus  consists  of  a  boiler  shell,  without  tubes  or  furnaces,  partially 
filled  with  water,  the  exhaust  steam  or  the  surplus  live  steam  from 
any  boiler  plant  being  taken  to  the  thermal  storage  tank,  where  it 
is  turned  into  the  water,  heating  it  to  a  temperature  corresponding  to 
that  of  the  steam,  the  water  being  used  afterwards  for  feeding  the 
boilers.  It  will  be  obvious  that  the  same  arrangement  as  rules  with 
Professor  Eateau's  apparatus,  would  rule  in  Mr.  Halpin's,  if  proper 
arrangement  is  made.  There  is  always  a  steam  space  within  the  boiler 
shell,  as  in  Professor  Eateau's  arrangement,  and  it  should  be  easy 
to  take  steam  from  the  thermal  storage  tank  in  place  of  water.  *As 
the  water  would  be  raised  to  a  temperature  considerably  above  that 
of  the  low-pressure  steam  employed  in  the  velocity  turbine,  this,  it 
appears  to  the  author,  should  be  able  to  be  obtained  by  any  arrange- 
ment providing  for  storage  of  steam  and  water,  in  which  the  tempera- 
ture of  the  water  was  raised  above  the  ordinary  temperature  at  which 
steam  evaporates  under  ordinary  atmospheric  pressures. 


Turbines  and  Condensing 

As  explained  in  Chapter  I.,  the  heat  that  can  be  extracted  from 
the  steam  is  as  large  between  the  ordinary  atmospheric  pressure  and 
29-inch  vacuum,  as  between  a  pressure  of  83  Ibs.  absolute  and  atmo- 
spheric pressure.  In  reciprocating  engines,  as  explained,  the  full 
steam  scale  cannot  be  utilized,  because  the  volume  of  the  steam 
increases  so  very  rapidly,  after  atmospheric  pressure  is  passed,  and 
particularly  on  the  lower  portions  of  the  scale,  that  the  engine  cylinders 
to  make  use  of  it  would  have  to  be  so  very  large  that  the  advantage 
would  be  lost.  In  reciprocating  engines,  25-inch  vacuum  is  the  limit 
at  which  condensation  is  economical,  and  then  only  providing  the  other 
points  that  have  been  mentioned  are  favourable.  With  turbines, 
however,  it  is  a  very  simple  matter  to  increase  the  size  of  the 
cylinder  in  which  the  turbine  revolves,  and  the  turbine  rotor,  and 
therefore  the  steam  can  be  utilized  at  as  low  a  pressure,  and  as  large 
a  volume,  as  can  be  obtained.  Hence,  condensing  is  of  great  import- 
ance in  steam  turbine  work,  because,  as  will  be  seen,  the  larger 
portion  of  the  work  is  done  by  the  steam  at  below  atmospheric 


328    STEAM   BOILERS,  ENGINES,   AND   TURBINES 

pressure.  The  advantages  of  high  vacua  with  steam  turbines  have 
been  questioned  by  reciprocating  engine  builders,  because  of  the 
increased  quantities  of  cooling  water  that  are  required.  This  is  dealt 
with  in  the  chapter  upon  condensers.  It  may  be  mentioned,  how- 
ever, that  Mr.  Parsons  claims  that  while  there  is  a  gain  of  4  per  cent. 
by  the  higher  vacua  obtained  by  his  special  apparatus,  the  cost  of 
obtaining  the  vacua  is  only  1  per  cent,  of  the  total  output. 


Turbines  and  Superheated  Steam 

The  question  of  superheated  steam  has  been  fully  dealt  with  in 
a  previous  part  of  the  book,  but  more  particularly  with  reference  to 
reciprocating  engines.  The  conditions  ruling  with  steam  turbines 
are  quite  different,  as  explained,  to  those  ruling  in  reciprocating 
engines,  and  there  should  be  no  cylinder  condensation,  or  anything 
corresponding  to  it.  The  containing  cylinder  of  the  turbine,  when 
once  warmed  up  by  the  entering  steam,  remains  at  a  certain  tempera- 
ture, corresponding  approximately  to  the  temperature  of  the  steam 
that  is  passing  through  it,  and  there  should  be  no  tendency  for  any 
portion  of  the  steam  or  vapour  to  condense,  by  coming  in  contact 
with  metals  at  a  lower  temperature.  On  the  other  hand,  however, 
superheating  of  steam  is  a  distinct  advantage  with  steam  turbines, 
but  mainly  for  another  reason.  Even  with  steam  turbines  having 
all  their  parts,  while  working,  at  certain  definite  temperatures,  it  is 
better  for  the  steam  to  enter  dry,  without  the  vapour  it  brings  over  from 
the  boiler,  as  water  loose  in  any  steam  system  is  always  troublesome. 
In  addition  to  that,  however,  superheated  steam  has  a  distinct 
advantage  over  saturated  steam,  in  that  it  does  not  so  readily  part 
with  its  heat  to  the  objects  with  which  it  comes  in  contact,  as  the 
blades  of  the  turbine,  the  blades  or  buckets  or  diaphragms  of  the 
turbine,  the  containing  cylinder,  etc.  According  to  Professor  Siebel, 
the  great  authority  on  refrigeration,  superheated  steam  has  a  less 
tendency  to  part  with  its  heat  to  objects  with  which  it  comes  in  contact 
than  saturated  steam,  in  the  proportion  of  one  to  forty;  hence  the 
use  of  superheated  steam  is  a  distinct  advantage.  In  addition,  there  is 
very  little  trouble  in  arranging  that  the  working  parts  of  the  steam 
turbine  that  are  exposed  to  the  high  temperatures  of  superheated 
steam,  shall  be  able  to  withstand  those  temperatures.  Further,  as 
no  lubrication  is  necessary  on  the  inside  of  the  steam  turbine  case, 
such  as  is  necessary  in  the  reciprocating  engine,  to  overcome  the 
friction  of  the  piston,  the  problem  of  a  lubricant  to  stand  the  high 
temperatures  which  arises  in  connection  with  the  lubricating  of 
reciprocating  cylinders  in  which  superheated  steam  is  employed,  does 
not  arise  here. 


PLATE  23A.— Complete  Contraflo  Condenser. 


PLATE  23s. — Contraflo  Condenser,  with  Air  Pump. 


[To  face  p.  328. 


THE  STEAM   TURBINE  329 

Incidentally  it  may  be  mentioned,  that  it  is  claimed  for  steam 
turbines,  that  the  exhaust  steam  is  not  contaminated  with  oil  from  the 
steam  turbine,  as  it  is  from  the  cylinder  of  a  reciprocating  engine, 
and  therefore  can  be  used  for  feeding  the  boilers  without  the  use  of 
oil  separators.  It  is  stated  even  that  the  condensed  water  from  the 
exhaust  of  steam  turbines  is  used  for  certain  purposes  where  distilled 
water  is  usually  employed.* 


CHAPTER  VI 

CONDENSING  PLANT 

The  Condenser 

THE  condenser  is  the  apparatus  in  which  the  steam  which  has  done  its 
work  in  the  engine  or  the  turbine  is  reconverted  into  water,  and  it  is 
of  very  great  importance  in  the  economy  of  steam  working.  As  was 
described  in  connection  with  the  working  of  reciprocating  steam 
engines,  after  the  piston  has  completed  its  stroke,  and  when  the  steam 
enters  on  its  other  side  to  cause  it  to  make  its  return  stroke,  the 
steam  which  remains  in  the  cylinder  from  the  previous  stroke  offers 
a  certain  resistance  to  the  return  of  the  piston,  this  being  known  as 
back  pressure.  Where  the  steam  is  allowed  simply  to  discharge  into 
the  atmosphere,  this  back  pressure  will  be  that  of  the  atmosphere, 
plus  something  in  addition,  the  unused  pressure  of  the  steam  itself, 
the  back  pressure  gradually  decreasing  as  the  steam  gets  away.  It 
can  be  seen,  however,  that  even  if  the  steam  offers  no  back  pressure 
to  the  piston,  if  the  atmospheric  pressure  or  a  portion  of  it  can  be 
removed,  the  work  the  piston  is  enabled  to  do  at  each  stroke  is 
increased,  and  this  is  what  is  accomplished  by  condensing,  the 
pressure  in  front  of  the  piston  being  reduced  in  the  latest  modern 
plants  to  as  low  as  1  Ib.  per  square  inch. 

With  steam  turbines,  also,  as  explained,  a  largely  increased  duty 
is  obtained  by  lowering  the  pressure  at  the  exhaust,  and  allowing  a 
larger  range  of  the  heat  scale  to  be  used. 

To  accomplish  this  the  heat  must  be  removed  from  the  steam, 
and  the  steam  reconverted  to  water.  It  will  be  remembered  that  the 
energy  present  in  the  steam  is  proportional  to  the  heat  that  has  been 
delivered  to  it,  and  that  as  the  steam  expands,  doing  work  on  the 
piston,  or  on  the  turbine,  its  temperature  lowers,  but  even  when  the 
pressure  is  lowered  to  the  very  low  figures  mentioned  above,  the  steam 
still  contains  a  large  quantity  of  heat  in  the  latent  form,  and  this 
must  be  removed  before  it  can  be  reconverted  to  water. 

The  condenser  is  practically  the  reverse  of  the  steam  feed- water 

330 


CONDENSING  PLANT  331 

heater.  In  the  feed-water  heater,  it  will  be  remembered,  the  heat  of 
the  steam  is  passed  to  the  water  through  pipes,  or  directly,  the  tem- 
perature of  the  water  being  raised  for  the  purpose  of  feeding  the 
boiler.  In  the  condenser  the  heat  of  the  steam  is  again  passed  to 
the  water,  the  temperature  of  which  is  raised,  but  it  is  for  the 
purpose  of  condensing  the  steam  and  of  depriving  it  of  all  its 
latent  heat. 

Forms  of  Condenser 

There  are  three  forms  of  condenser,  known  respectively  as  the 
"  Surface  condenser,"  the  "  Jet  condenser,"  and  the  "  Ejector  con- 
denser.", 

The  Surface  Condenser 

There  are  two  forms  of  surface  condenser,  the  "  enclosed  "  and 
the  "  evaporative."  The  enclosed  surface  condenser  is  practically  the 
reverse  of  the  enclosed  feed-water  heater,  is  constructed  on  very  much 
the  same  lines,  and  is  sometimes  combined  with  it.  There  is  an 
iron  box,  which  may  be  of  any  convenient  form,  cylindrical  or 
rectangular  in  section,  the  cylindrical  form  is  a  favourite  ;  and  there 
are  tube  plates  at  each  end  of  the  box,  arranged  to  hold  the  ends 
of  the  tubes,  which  are  of  brass  or  gun-metal,  according  to  the  fancy 
of  the  maker,  and  the  water  with  which  it  is  likely  to  have  to  deal. 
The  water  enters  at  one  end  of  the  box,  passes  through  the  tubes, 
and  out  at  the  other  end,  the  steam  entering  somewhere  near  the 
middle  of  the  box  on  one  side,  passing  over  the  outer  surface  of  the 
tubes,  and  out  at  the  other  side,  the  steam  being  condensed  to  water 
in  the  process,  and  being  drawn  off  by  the  air  pump,  as  will  be 
explained. 

As  with  feed- water  heaters,  the  reverse  of  this  arrangement  some- 
times holds,  the  steam  passing  through  the  tubes,  and  the  water  pass- 
ing on  the  outside,  but  the  more  frequent  arrangement  is  for  the 
water  to  pass  through  the  tubes. 

Two  pumps  are  required  to  complete  the  surface  condenser  plant, 
in  addition  to  the  apparatus  just  described,  a  pump  to  circulate  the 
cooling  water  through  the  tubes,  and  a  pump  to  withdraw  the  con- 
densed steam,  and  the  air  which  comes  over  with  the  steam  from  the 
body  of  the  apparatus.  The  latter  is  called  the  air  pump,  and  it  is 
of  the  utmost  importance  that  it  shall  be  thoroughly  efficient.  In 
fact,  the  extraction  of  the  air  from  the  space  in  which  the  steam  is 
condensed  forms  one  of  the  greatest  difficulties  in  the  matter  of  con- 
densation, especially  with  very  low  pressures,  or,  as  it  is  usually 
expressed,  high  vacua.  Mr.  Charles  Parsons,  who  has  worked  at  the 


332    STEAM   BOILERS,  ENGINES,  AND   TURBINES 

problem  in  connection  with  his  steam  turbine,  has  found  that  the 
presence  of  air  in  the  condenser  "  blankets  "  the  particles  of  steam, 
as  he  expresses  it.  That  is  to  say,  particles  of  air  surround  particles 
of  steam,  and  prevent  the  transmission  of  heat  from  the  steam  to  the 
cooling  water,  or  cooling  surface,  and  thereby  increase  the  difficulty 
of  the  formation  of  the  vacuum. 

It  will  be  remembered  that  at  atmospheric  pressure  the  steam 
has  a  pressure  of  14-7  Ibs.  to  the  square  inch,  and  by  the  action  of  an 
efficient  condenser  this  pressure  is  gradually  reduced  to,  in  the  cases 
of  very  efficient  apparatus,  as  low  as  1  Ib.  per  square  inch.  As  the 
pressure  of  the  atmosphere  balances  the  pressure  of  steam  at  atmo- 
spheric pressure,  and  as  the  pressure  of  the  atmosphere  is  measured 
by  the  column  of  mercury  29*96  inches ;  as  the  pressure  of  steam  is 
lowered,  the  column  of  mercury  that  it  would  balance  is  also 
lowered,  and  it  is  usual  to  express  the  work  done  in  a  condenser  in 
terms  of  inches  of  vacuum.  Thus,  if  the  whole  of  the  pressure  of 
the  steam  can  be  removed,  the  vacuum  would  be  expressed  as  29*96 
inches  at  sea  level.  On  the  other  hand,  the  gradual  lowering  of  the 
pressure  is  expressed  by  gradual  increase  of  the  vacuum  in  inches. 
Thus,  it  is  usual  to  talk  of  10  inches,  20  inches,  25  inches  of  vacuum, 
and  so  on,  29*96  inches  being  the  highest  possible  under  normal  con- 
ditions at  sea  level,  and  29  inches  being  practically  the  highest 
vacuum  that  has  yet  been  obtained  in  ordinary  work.  Twenty-five 
inches  was  considered  a  high  vacuum  with  reciprocating  engines,  it 
corresponding  approximately  to  a  lowering  of  the  pressure  of  the 
steam  by  12  J  Ibs.  per  square  inch ;  but  since  the  advent  of  the  turbine, 
and  the  improvements  that  have  been  made  in  apparatus  for  pro- 
ducing good  vacuum  by  Mr.  Parsons  and  others,  28£  inches  is  very 
common. 

In  the  production  of  a  good  vacuum  the  air  pump  plays  a  very 
important  part  indeed.  The  usual  form  of  the  air  pump  is  described 
later.  If  the  air  pump  does  not  pull  out  all  the  air  as  well  as  the 
condensed  steam,  the  vacuum  is  not  as  perfect  as  it  otherwise 
would  be. 

The  circulating  pump  is  also  of  considerable  importance,  though 
it  is  necessarily  much  simpler  than  the  air  pump.  It  will  be  under- 
stood that  in  order  to  extract  the  heat  from  the  steam  it  is  necessary 
to  pass  a  certain  quantity  of  water  through  the  condenser,  and  that 
the  quantity  of  water  required  will  depend  inversely  upon  its  own 
temperature  and  directly  upon  the  inches  of  vacuum  required,  the 
quantity  increasing  very  rapidly  with  high  vacua,  as  explained  more 
fully  on  pages  351,  et  seq.  It  will  be  understood  that  the  cooling 
water  can  only  be  raised  to  a  certain  temperature  in  its  passage 
through  the  condenser.  In  practice,  150°  F.  is  usually  the  limit, 
though  on  occasion  cooling  water  is  sometimes  raised  to  as  much  as 


CONDENSING  PLANT 


333 


175°  F. ;  but  it  is  not  economical  to  do  so.  This  being  so,  and  as 
every  gallon  of  water  absorbs  10  heat  units  for  every  degree  F.  of 
increase  of  temperature,  it  will  be  evident  that  the  lower  the  tempera- 
ture at  which  the  water  enters,  the  smaller  will  be  the  total  quantity 
required.  Thus,  with  the  water  at  50°  F.,  each  gallon  passed  through 
the  condenser  should  absorb  1000  heat  units,  while  if  only  water  of 
100°  is  available,  each  gallon  will  only  absorb  500  units,  and  double 
the  quantity  must  be  employed.  Hence  will  be  seen  the  reason  for 


FIG  .  158. — Sectional  drawing  of  Surface  Condenser  and  Cooling  Tower,  with  Accessories. 

employing  cooling  towers  and  other  apparatus  for  the  circulating 
water. 

As  explained  in  dealing  with  the  heating  of  feed  water,  the  cool- 
ing water  from  the  condenser  is  frequently  used  for  the  boiler  feed, 
since  it  is  not  impregnated  with  oil,  etc.,  but  this  can  only  be  where 
cooling  water  is  plentiful,  as  where  the  boiler  is  fixed  close  to  a  river 
or  canal,  from  which  unlimited  water  may  be  taken.  In  a  great 
many  instances,  unfortunately,  water  is  very  expensive,  so  expensive 
in  some  cases  that  the  saving  in  coal  from  the  lowered  pressure  in 
front  of  the  piston  is  more  than  balanced  by  the  cost  of  the  water  and 
other  expenses  for  cooling.  In  these  cases,  where  condensation  is 
carried  out,  some  form  of  cooling  appliance  is  employed,  the  cooling 
water  being  used  over  and  over  again.  Fig.  158  is  a  sectional 


334    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

drawing  of  a  surface  condenser  with  a  cooling  tower.  The  quantities 
of  cooling  water  employed  with  the  ordinary  condensers  are  given 
further  on. 


The  Evaporative  Surface  Condenser 

In  the  evaporative  condenser  the  property  possessed  by  air  of 
absorbing  the  vapour  of  water  is  made  use  of  to  reduce  the  quantity 
of  the  cooling  water.  In  this  apparatus  the  steam  to  be  condensed 
passes  through  a  grid  of  pipes,  as  shown  in  Fig.  159,  which  is  one  of 
Ledward's  evaporative  condensers,  and  a  stream  of  water  is  made  to 


FIG.  159. — Ledward's  Evaporative  Surface  Condenser.   S  is  the  Exhaust  Steam  Pipe ; 
W  the  Cooling-water  Pipe ;  C  the  Condensed  Steam  Pipe. 

trickle  down  over  the  outside  surface  of  the  pipes,  the  steam  being 
condensed  on  the  inside,  and  being  withdrawn  by  the  air  pump,  as  in 
the  enclosed  surface  condenser.  The  usual  arrangement  is :  A  pipe 
having  perforations  on  its  under  side  is  fixed  above  each  of  the  rows 
of  pipe  forming  the  grid,  and  a  trough  is  fixed  below  the  whole  of  the 
grids,  so  as  to  catch  all  the  water  that  is  not  evaporated,  after  it  has 
passed  over  the  pipes.  The  water  is  forced  out  of  the  perforations  in 
the  upper  pipe  in  the  form  of  very  fine  jets,  and  it  is  made  to  trickle 
over  the  outside  of  the  condenser  pipes  in  a  very  thin  stream,  so  that 
it  may  be  exposed  to  the  full  action  of  the  atmosphere.  The  cooling 
action  is  twofold.  The  water  absorbs  a  certain  quantity  of  heat 
from  the  pipes  over  which  it  passes  in  raising  its  own  temperature, 
but  a  very  much  larger  quantity  of  heat  is  extracted  from  the  water, 
and  through  it  from  the  pipes,  and  thence  from  the  steam  by  the 
evaporation  of  a  small  quantity  of  the  cooling  water.  Each  pound 


CONDENSING   PLANT  335 

of  water  in  forming  vapour  will  absorb  in  the  neighbourhood  of  900 
units,  and  this  is  taken  almost  entirely  from  the  pipes  and  the  con- 
densed steam,  hence  the  quantity  of  water  required  is  very  much  less 
than  with  the  enclosed  form.  The  cooling  effect  of  the  evaporative 
condenser  depends  upon  the  temperature  at  which  the  water  is  first 
delivered  to  the  pipes,  also  upon  the  temperature  and  degree  of 
humidity  of  the  atmosphere,  and  upon  the  force  of  the  wind.  It  is 
usual  to  fix  evaporative  condensers  in  positions  where  the  pipes 
and  the  water  will  feel  the  force  of  any  wind  that  may  be  blowing, 
but  so  that  the  water  will  not  be  blown  away  to  any  extent.  The 
cooling  effect  of  the  water  itself,  by  reason  of  its  rise  of  temperature, 
forms  only  a  small  portion  of  the  total  cooling.  The  cooling  effect  of 
the  evaporation  depends  upon  the  humidity  of  the  atmosphere,  as 
explained  in  Chapter  I.,  upon  the  tension  of  the  vapour  issuing  from 
the  water,  and  upon  that  present  in  the  atmosphere.  The  ability  of 
the  atmosphere  to  absorb  moisture  increases  with  the  temperature, 
as  already  explained  in  Chapter  I. ;  but,  on  the  other  hand,  the 
atmosphere  is  often  so  full  of  moisture  on  the  days  that  we  call 
muggy,  that  it  is  unable  to  absorb  any  more.  In  those  cases  there 
may  be  even  deposit  from  the  atmosphere  in  the  cooling  water.  The 
action  of  the  wind  has  a  most  important  bearing  upon  the  quantity 
of  water  required,  because,  it  will  be  understood,  each  cubic  foot  of 
air,  at  a  certain  temperature  and  a  certain  humidity,  is  able  to  absorb 
a  certain  quantity  of  vapour,  and  therefore  the  rapid  passage  of  an 
air  current  across  the  grid  of  pipes  over  which  the  water  is  passing 
increases  the  cooling  effect  due  to  the  atmosphere  alone.  The  author 
has  been  told  of  cases  of  evaporative  condensers  exposed  to  cold 
winds  where  the  cooling  water  was  colder  after  it  had  passed  over 
the  condenser  than  before  it  was  delivered  to  it. 

The  quantity  of  water  used  with  evaporative  condensers  varies 
from  fifteen  times  the  weight  of  steam  condensed  with  dry,  warm  air, 
such  as  would  rule  in  parts  of  America  and  Canada  during  the 
summer,  to  forty  times  with  very  muggy  air.  A  certain  quantity 
of  the  cooling  water  is  lost  by  evaporation,  the  amount  varying 
with  the  conditions. 


Fraser's  Evaporative  Condenser 

This  is  an  apparatus  in  which  the  principle  of  cooling  by  evapora- 
tion is  carried  out  in  a  novel  manner.  The  apparatus  is  enclosed  in 
place  of  being  open  to  the  atmosphere,  as  in  the  case  of  the  evaporative 
condensers  described  above.  The  pipes  through  which  the  steam 
passes  are  fixed  inside  a  case,  arranged  in  a  stack  in  the  usual  way. 
The  cooling  water  is  pumped  to  the  top  by  a  centrifugal  pump,  and 


336    STEAM  BOILERS,   ENGINES,  AND   TURBINES 

is  discharged  over  the  top  of  the  condenser  tubes  by  spraying  nozzles 
1  inch  in  diameter,  the  water  falling  over  the  outside  of  the  tubes  as 
in  other  forms  of  evaporative  condenser ;  but  in  place  of  depending 
upon  atmospheric  air  for  the  evaporation,  fans  are  fixed  at  the  base 
of  the  apparatus,  and  these  drive  a  current  of  air  up  through 
the  tubes,  meeting  the  spray  of  water  descending  over  them,  and 
causing  evaporation  in  the  same  manner  as  in  the  open  evapo- 
rating condenser.  It  is  claimed  that  this  arrangement  is  an 
improvement  on  the  open  evaporative  condenser,  as  the  tubes  are  not 
exposed  to  the  dust,  etc.,  that  is  in  the  atmosphere,  and  that  is  often 
deposited  upon  them,  leading  to  the  formation  of  a  scale  that  resists 
the  passage  of  heat  through  them,  in  the  same  manner  as  has  been 
explained  in  connection  with  boiler  tubes.  The  tubes  are  of  brass, 
f-inch  external  diameter,  similar  to  those  employed  in  marine  con- 
densers, fixed  in  tube  plates  by  brass  ferrules  and  tape  packing ;  and 
it  is  claimed  that  the  expansion  and  contraction  of  the  tubes  causes 
any  scale  that  is  formed  upon  them  owing  to  hardness  of  water,  to 
crack  and  be  thrown  off,  leaving  the  tubes  clean.  It  is  also  claimed 
that,  being  enclosed,  this  condenser  is  not  affected  by  the  direct  rays 
of  the  sun,  nor  by  winds,  and  is  comparatively  independent  of 
variable  atmospheric  conditions.  It  is  also  claimed  that  the  power 
required  to  drive  the  fans  is  very  small,  as  very  little  obstruction  is 
caused  by  the  water  falling  over  the  tubes,  the  water-gauge  being,  it  is 
stated,  under  2  J-  tenths  of  an  inch  ;  and,  further,  that  the  condenser 
does  not  make  itself  a  nuisance  in  the  neighbourhood  by  throwing 
out  spray. 

In  connection  with  this  condenser  a  double-acting  air  pump, 
specially  designed,  is  employed. 


The  Wheeler  Surface  Condenser 

In  the  Wheeler  condenser,  a  sectional  drawing  of  which  is  shown 
in  Fig.  160,  and  which  is  made  either  in  circular  or  rectangular  form 
— preferably  rectangular, — the  condenser  vessel,  as  seen,  is  divided 
into  two  portions,  the  water  passing  through  the  two  in  succession. 
The  steam,  as  will  be  seen,  enters  at  the  top,  the  condensed  steam 
leaving  at  the  bottom,  and  the  cooling  water  enters  by  the  inlet  at  the 
bottom  on  the  right,  passes  through  the  lower  bank  of  tubes,  then  through 
the  upper  bank  of  tubes,  and  out  at  the  water  outlet  at  the  top  on  the 
right.  It  will  be  noticed  that  the  principle  upon  which  all  apparatus 
in  which  heat  passes  from  one  fluid  to  another  are  constructed,  is 
observed  in  this,  the  hottest  steam  passing  over  the  tubes  in  which 
the  hottest  water  is  circulating,  and  the  coolest  steam  or  the  con- 
densed water  meeting  the  coldest  water  as  it  enters. 


PLATE  24A. — Condensing  Plant  for  a  Pair  of  large  Blowing  Engines  at  a  Steel  Works. 
The  Condenser  is  seen  on  the  Wall  of  the  Engine-house. 


PLATE  24B.— Tangye  Duplex  Double-acting  Steam  Pump. 


uce  p.  336. 


CONDENSING  PLANT 


337 


In  the  Wheeler 
condenser  also,  the 
tubes  are  sometimes 
held  between  tube 
plates,  and  sometimes 
are  arranged  on  the 
double  -  tube  system, 
the  tubes  in  that  case 
only  being  held  at  one 
end,  and  being  free  to 
expand  and  contract. 

In  one  form  of  the 
apparatus  the  conden- 
ser, the  air  pump,  and 
the  circulating  water 
pump  are  mounted 
together  upon  one  bed 
plate,  the  inlet  tube 
for  the  water  and  the 
outlet  tube  for  the 
steam  forming  practi- 
cally the  supports  of 
the  condenser  cham- 
ber. A  single  steam 
cylinder  drives  both 
the  water  and  the  air 
pump  pistons. 

In  another  appa- 
ratus the  Wheeler 
Company  have  com- 
bined the  feed-water 
heater  with  the  con- 
denser. The  vessel 
forming  the  combined 
apparatus  is  divided 
into  two,  which  are 
constructed  practi- 
cally alike,  with  tubes 
held  between  tube 
plates,  the  feed  water 
for  the  boiler  circu- 
lating through  the 
tubes  in  the  upper 
portion,  while  the 
cooling  water  for  the 


310H  ONVH 


338    STEAM  BOILERS,  ENGINES,  AND  TURBINES 

condenser  itself  circulates  in  the  lower  portion,  passing  through  the 
banks  of  tubes  in  succession.  The  exhaust  steam  enters  at  the  top, 
and  is  guided  by  baffles  to  the  right  and  left  of  the  entry,  then 
passing  over  the  feed-water  tubes  and  the  condenser  tubes  in 
succession.  Where  some  of  the  circulating  water  is  employed  as  feed 
water,  it  will  be  seen  that  the  arrangement  can  be  carried  out  very 
conveniently. 


Open  Tank  Surface  Condensers 

The  Klein  Engineering  Company,  the  Balcke  Company,  and 
others,  construct  a  modified  surface  condenser,  in  which  the  steam 
circulates  inside  the  tubes  in  place  of  outside,  the  tubes  being  built 
into  stacks,  and  placed  in  open  brickwork  tanks,  the  cooling  water 
being  caused  to  pass  slowly  through  the  tanks  and  around  the  tubes 
by  the  circulating  pump  in  the  usual  way. 

A  modification  of  this  is  made  by  the  Klein  Co.  for  laying  in  the 
beds  of  streams.  A  brickwork  tank  is  built  in  the  bed  of  the  stream, 
and  the  water  is  allowed  to  circulate  through  the  tank  under  the 
force  of  the  stream. 


The  Contraf lo  Condenser 

This  is  a  form  of  surface  condenser  introduced  within  the  last 
few  years    by   Messrs.   Kichardson,   Westgarth    &    Co.,   in   which 


FIG.  161.— Sectional  drawings  of  Contraflo  Condenser,  showing  the  divisions  of  the 
Condenser,  the  Hot  Well,  etc. 

certain  novel  features  are  introduced  that  are  claimed  to  increase 
the  efficiency  of  the  apparatus.  The  complete  apparatus  is  shown  in 
Plates  23A  and  23s,  and  sections  of  it  in  Fig,  161.  From  the  sectional 


CONDENSING  PLANt  339 

drawings  it  will  be  seen  that  it  is  practically  three  separate  condensers, 
each  fitted  with  pipes  for  the  water  to  circulate  in,  on  the  lines  of  the 
ordinary  surface  condenser,  but  the  three  condensers  are  arranged  in 
series,  that  is  to  say,  the  steam  passes  through  the  three,  one  after 
the  other,  the  condensed  water  finally  finding  its  way  to  the  hot 
well  shown  at  the  bottom.  In  addition,  each  of  the  separate  con- 
densing chambers  is  drained  of  its  water  by  separate  pipes  com- 
municating with  the  hot  well.  The  steam  enters  by  the  steam  pipe 
at  the  top,  passes  over  and  between  the  condensing  pipes  in  the 
upper  chamber,  then  it  passes  by  the  vapour-distribution  chamber, 
as  it  is  termed,  shown  on  the  left  in  the  transverse  vertical  section 
on  the  left  of  Fig.  161,  into  the  second  condensing  chamber.  It 
passes  over  the  pipes  in  the  second  condensing  chamber,  and  thence 
by  way  of  the  vapour- distribution  chamber  on  the  right,  to  the  third 
and  lowest  condensing  chamber.  The  vapour-distribution  chambers, 
as  will  be  seen,  are  really  communications  between  the  different  con- 
densing chambers.  The  idea  in  the  mind  of  the  inventor  of  the 
Contraflo  condenser  is,  that  the  major  portion  of  the  condensation 
takes  place  in  the  neighbourhood  of  the  upper  condensing  pipes, 
where  the  first  cooling  takes  place,  and  that  if  the  condensed  water 
formed  there  can  be  drained  away,  there  is  less  chance  of  any  portion 
of  it  being  re-evaporated.  One  of  the  difficulties  in  connection  with 
condensers  is,  any  water  that  is  formed  by  condensation  when  the 
steam  enters  a  condenser  may  be  re-evaporated  into  steam,  and  have 
to  be  recondensed  if  the  conditions  are  favourable.  It  was  explained 
in  the  first  chapter  that  the  formation  of  steam  depends  upon  the 
heat  present,  and  upon  the  pressure  to  which  the  surface  of  the  water 
from  which  steam  is  to  be  made  is  exposed.  Lowering  the  pressure 
allows  steam  to  be  formed  at  a  lower  temperature  than  with  higher 
pressure,  and  as  it  is  a  necessity  of  the  case  that  the  pressure  in 
the  condenser  shall  be  continually  lowered  by  the  air  pump,  it 
follows  that  the  conditions  favourable  for  the  reformation  of  steam 
may  occur  during  the  later  portion  of  the  passage  of  the  condensed 
steam  through  the  condenser. 

The  usual  counter  current  arrangement  is  adopted  in  the  Contraflo 
condenser.  That  is  to  say,  the  cooling  water  enters  the  pipes  of  the 
lowest  portion  of  the  condenser,  and  is  forced  upwards,  passing  to 
and  fro  in  successive  lengths  of  pipes,  finally  issuing  at  the  top ;  the 
steam,  passing  downwards  from  the  top,  and  issuing  into  the  hot 
well.  Thus,  the  hottest  water,  that  which  has  already  done  work  in 
cooling  the  steam  and  water  below  it,  meets  the  hottest  steam,  and 
the  coldest  steam  or  condensed  water  meets  the  coldest  cooling 
water. 


340    STEAM   BOILERS,  ENGINES,  AND  TURBINES 


Jet  Condensers 

The  jet  condenser  is  practically  the  reverse  of  the  open  feed- 
water  heater,  but  the  apparatus  is  designed  primarily  for  condensing 
the  steam,  and  not  for  heating  the  water,  though  the  water  is 
necessarily  heated  in  the  process.  The  jet  condenser  consists  of  a 
vessel  of  various  forms,  into  which  the  steam  is  brought,  and  also 
into  which  the  cooling  water  is  brought  in  the  form  of  a  spray.  The 
steam  meeting  the  water,  gives  up  its  heat  to  the  water,  is  condensed, 
and  the  two  are  pumped  out  together  by  the  air  pump,  just  as  in  the 
surface  condenser. 

There  are  two  methods  of  arranging  the  jet  condenser,  known  as 
the  parallel-current  and  counter-current  apparatus.  In  the  parallel- 
current  apparatus  the  steam  and  water  enter  more  or  less  opposite 
each  other,  and  flow  in  a  parallel  direction  through  the  condenser 
vessel,  the  two  mixing,  and  the  water  being  condensed  on  the  way.  In 
the  counter-current  condenser,  the  steam  enters  from  one  side,  and 
the  water  from  the  other,  and  the  two  flowing  in  opposite  directions, 
mix  as  before.  The  vessel  into  which  the  steam  and  water  enter  has 
various  forms.  Usually  with  the  counter-current  design,  it  is  fixed 
in  a  horizontal  position,  and  consists  of  a  cylinder,  the  steam  entering 
from  one  end,  the  water  from  the  other,  and  the  condensed  water 
being  pumped  out  from  the  end  at  which  the  water  enters.  In  one 
form  of  the  counter-current  jet  condenser,  made  by  Messrs.  Balcke, 
the  main  condensing  vessel  consists  of  a  horizontal  cylinder,  the 
steam  entering  it  by  a  steam  pipe  on  the  left,  and  the  water  entering 
through  a  dome  above  the  right-hand  portion  of  the  condenser.  The 
object  of  the  dome  is  to  separate  the  air  that  comes  in  with  the  steam 
from  the  water,  and  the  operation  of  the  condenser  is  as  follows :  The 
steam  entering  the  main  condensing  vessel  meets  the  large  body  of 
water  below,  and  nearly  the  whole  of  it  is  condensed.  A  portion,  how- 
ever, passes  onward  and  enters  the  dome,  where  it  meets  the  cold  spray 
produced  in  the  dome,  and  is  condensed,  the  air  and  incondensible 
gases  passing  upwards  and  being  pumped  out  by  the  air  pump  con- 
nected to  a  pipe  at  the  top.  The  condensed  water  is  pumped  out 
through  a  pipe  at  the  bottom  by  a  pump,  and  is  delivered  to  the  air 
cooler,  the  cooling  water  for  the  condenser  being  taken  from  a  tank 
on  the  one  side  of  the  cooling  tower,  into  which  the  water  from  the 
bottom  of  the  tower  overflows. 

It  is  claimed  that  with  the  combined  arrangement  of  jet  condenser 
and  cooling  tower,  the  water  lost  by  evaporation  in  the  process  of 
cooling  is  made  up  by  that  condensed  from  the  exhaust  steam. 

Two  pumps  are  required  for  the  jet  condenser,  the  air  pump 
which  will  be  of  a  similar  form  to  that  employed  with  the  surface 


CONDENSING   PLANT 


341 


condenser,  but  a  little  larger,  as  it  has  to  deal  with  the  cooling  water 
as  well  as  with  the  water  formed  from  condensed  steam,  and  a  pump 
to  deliver  the  cooling  water  itself,  which  must  be  arranged  in  the 
form  of  a  spray. 

The  jet  condenser  is  more  efficient  than  the  surface  condenser,  so 
far  as  the  quantity  of  water  required  for  cooling  is  concerned,  but  it 
is  not  as  well  liked  as  the  surface  condenser. 


The    Mi rrlees- Watson 
denser 


Jet    Con- 


in  this  apparatus  a  new  departure  has  been 
struck.  The  condenser  vessel  contains  a  number 
of  trays,  fixed  one  above  the  other,  and  the  water 
enters  the  condenser  at  the  top,  and  is  broken 
up  by  falling  over  the  trays,  very  much  after 
the  manner  of  the  arrangements  made  in  some 
cooling  towers.  The  steam  enters  at  the  bottom, 
and  is  obliged  to  pass  through  the  trays.  The 
air  is  drawn  out  from  the  upper  part  of  the 
condenser,  and  is  therefore  at  its  minimum 
volume,  this  applying  to  other  forms  of  jet  con- 
denser where  this  arrangement  rules,  while  the 
condensed  water  is  pumped  out  at  the  bottom. 


FIG.  162. — Section  of  Worthington  Jet  Condenser  and  Pump. 

The  Worthington  Jet  Condenser 

The  Worthington  jet  condenser,  with  its  pump,  is  shown  in  section 
in  Fig.  162,  and  fully  in  Fig.  163.     It  will  be  seen  that  the  condensing 


342     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

vessel  is  cone-shaped,  the  exhaust  steam  entering  by  the  pipe  A  on  the 
right,  and  the  cooling  water  by  the  pipe  B  on  the  left.  The  entrance 
B  must  not  be  more  than  20  feet  above  the  surface  of  the  water  supply 


FIG.  163. — Worthington  Jet  Condenser  for  1500  H.P.,  with  Pump. 

when  used  with  steam  engines.  The  water  jet  is  broken  up  into  a 
fine  spray  before  it  enters  the  condensing  vessel  by  means  of  the 
spray  pipe  C,  into  which  the  pipe  B  enters,  and  the  spraying  cone  D. 
The  pump  shown  is  of  the  piston  type,  driven  by  the  steam  cylinder 


CONDENSING  PLANT 


343 


ATM. 
SAFE 


"K,  and  constructed  generally  on  the  lines  of  the  Worthington  pumps. 
The  Worthington  jet  condenser  pump  is  sometimes  worked  by  a 
compound  or  triple-expansion  steam 
cylinder,  on  the  lines  of  the  Worth- 
ington pumping  engines  of  those 
types,  the  piston  rod  of  the  high- 
pressure  cylinder  being  connected 
to  the  pump  rod,  which  also  carries 
a  cross  head,  through  which  con- 
nection is  made  to  the  low-pressure 
piston,  the  low-pressure  and  inter- 
mediate-pressure pistons  being  con- 
nected by  one  rod. 

The  pump  described  above  is 
the  air  pump  of  the  condenser,  and 
it  is  claimed  that  it  performs  the 
office  of  air  pump  quite  as  well  as 
those  specially  designed  for  the 
purpose,  the  pump  being  specially 
arranged  to  deal  with  the  air  and 
water.  The  water  cylinders  are  lined 
with  composition,  and  the  glands 
and  the  stuffing  boxes  and  the  valve 
seats,  etc.,  are  of  the  same  material. 

The  velocity  with  which  the 
steam  enters  the  cone  F  of  the 
condenser,  it  is  claimed,  carries 
with  it  the  water  and  all  the  air  or 
uncondensible  vapour  that  has  come 
over  with  it,  the  air  and  water  being 
fully  dealt  with  by  the  piston  pump, 
and  being  discharged  through  the 
valves  shown  at  H  and  I,  and  the 
pipe  J.,  in  Fig.  162. 


The   Ejector  Condenser 

In  the  ejector  condenser,  forms 


of  which  are  shown   in    Figs.   164 


FIG.  164.— Section  of  Led  ward  Ejector 
Condenser,   with   three-way  auto- 
matic Valve,  providing  for  exhaust- 
,  ing  to  the  atmosphere  if  required. 

and    165,   the   action  is   somewhat 

similar    to    that    of    the    injector, 

but  reversed.  In  the  ejector  condenser  a  stream  of  water  is  kept 
continually  pouring  through  a  vessel,  as  shown,  into  which  the 
exhaust  steam  is  delivered.  The  passage  of  the  stream  of  water 


344    STEAM   BOILERS,  ENGINES,   AND  TURBINES 

through  the  apparatus  draws  the  exhaust  steam  after  it,  in  the 
well-known  injector  manner,  and  the  steam  meeting  the  water,  is 
immediately  condensed  and  passes  off  with  it.  The  ejector  condenser 
has  the  great  advantage  of  being  exceedingly  simple.  Only  one 


FIG.  165.— Diagram  of  arrangement  of  Steam  and  Water  Pipes,  with  Ledward's 

Ejector  Condenser. 

pump  is  required,  that  for  providing  the  stream  of  cooling  water, 
which  is  allowed  to  run  away,  or  is  used  over  again,  as  may  be 


arranged. 


The   Barometric  Condenser 


The  barometric  condenser  is  practically  a  modification  of  the 
ejector  condenser.  The  arrangement  is  shown  in  Fig.  166,  and  the 
condenser  vessel  in  section  in  Fig.  167.  It  takes  its  name  from 
the  fact  that  a  column  of  water  of  the  height  equivalent  to  the 
mercurial  barometer — that  is,  giving  the  same  pressure,  147  Ibs.  to 
the  square  inch,  or  as  the  ordinary  29*96  inches  of  the  mercurial 
barometer — is  employed  to  do  the  work  that  is  performed  in  other 
types  of  condenser  by  the  air  pump.  The  condenser  itself  is  fixed 
at  the  top  of  a  pipe  about  30  feet  high,  and  the  exhaust  steam  is  led 


PLATE  25A.— A  Pair  of  Vertical  Double-acting  Pumps  for  circulating  the  Condensing 
Water,  by  tbe  Mirrlees  Watson  Co. 


PLATE  25B.  — 
Hall's  Verti- 
cal Duplex 
Steam  Pump. 


PLATE  25c. — Surface  Condenser  with  Two- 
cylinder  Edwards'  Air  Pump,  Centri- 
fugal Circulating  Pump,  both  driven  by 
one  Electric  Motor,  and  all  on  one  bed- 
plate. 


PLATE      25D.— 
Hall's       Single 
Vertical  Steam 
Pump. 
[To  face  p.  344. 


CONDENSING   PLANT 


345 


up  another  pipe,  standing  by  the  side  of  the  condenser  pipe,  to  a 
point  a  few  feet  above  the  condenser.  The  top  of  the  exhaust- 
steam  pipe  is  provided  with  a  relief  valve,  and  usually  an  exhaust 


RELIEF  VALVE 


FIG.  166. — Arrangement  of  Pipes,  Pumps,  etc.,  of  Bulkley  Barometric  Condenser, 
connected  to  a  Steam  Turbine. 

head,  on  something  the  lines  that  have  been  described  with  other 
exhaust  heads.  The  bottom  of  the  condenser  pipe  is  carried  nearly 
to  the  bottom  of  a  vessel  called  the  hot  well,  into  which  the  con- 
densed steam  and  the  condensing  water  is  delivered,  and  from  which 


346     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

it  overflows  into  any  receptacle  that  may  be  provided  for  it.  The 
hot  well  is  usually  covered,  and  it  is  required  to  be  waterproof,  that 
is  to  say,  no  other  water  must  come  into  it,  except  that  delivered 
from  the  condenser.  The  cooling  water  may  be  delivered  to  the 
condenser  from  a  tank  at  a  height  that  will  allow  the  water  to  run 
into  the  condenser  by  gravity,  or,  where  that  is  not  available,  it  may 


FIG.  167. — Sectional  Diagram  of  the  Barometric  Tube  Condenser,  made  by  Williamson 

Bros.,  of  Philadelphia. 

be  pumped  up  by  any  convenient  pump,  centrifugal  or  otherwise, 
driven  by  any  convenient  source  of  power.  The  pump,  though  it 
has  to  deliver  the  water  to  the  condenser  at  about  30  feet  above  the 
hot  well,  has  not  really  to  lift  the  water  that  height,  the  partial 
vacuum  in  the  condenser  pipe  assisting  the  lift  in  the  pump  delivery 
pipe  to  the  extent  usually  of  about  22  feet,  so  that  the  lift  of  the  pump 
is  only  about  7  or  8  feet.  The  water  is  carried  into  the  condenser 


CONDENSING   PLANT 


347 


in  the  form  of  a  hollow  cylindrical  sheet  or  jet,  and  the  steam 
is  delivered  in  the  middle  of  the  water  jet  by  a  cone,  in  the  well- 
known  injector  manner.  The  passage  of  the  water  down  the  tube 
draws  the  steam  up  the  exhaust  and  down  the  barometric  condenser 
tube,  the  steam  combining  with  the  water,  and  the  velocity  acquired 
by  the  water  in  falling  being  sufficient  to  draw  down  the  air  which 
comes  over  with  the  steam,  as  well  as  the  exhaust  steam  itself.  It 
will  be  seen  that  the  great  advantage  obtained  by  the  use  of  the 
barometric  condenser  is  the  extinction  of  the  air  pump. 

In  some  forms  of  the  apparatus  an  air  pump  is  employed  as  well. 


Parsons  Vacuum  Augmenter 

The  importance  of  a  high  vacuum  for  steam  turbines  has  been 
mentioned  in  another  portion  of  the  book.   The  difficulty  of  obtaining 


FIG.  168. — Section  of  Parsons  Vacuum  Augmenter. 

high  vacua  is  dealt  with  later.  It  requires  a  considerably  increased 
quantity  of  cooling  water,  a  larger  surface  in  the  condenser,  in  pro- 
portion to  the  quantity  of  steam  to  be  condensed,  and  a  higher 
velocity  of  the  cooling  water.  In  addition,  a  larger  air  pump  is  also 
required,  as  when  high  vacua  are  reached,  the  air  is  more  important 
than  at  any  part  of  the  condensing  cycle.  With  all  these  arrange- 
ments, however,  it  was  till  recently  only  possible  to  obtain  a  vacuum 
of  from  27J  to  28  inches  of  mercury,  and  to  meet  the  case,  Mr. 
Parsons  has  worked  out  an  apparatus,  shown  in  section  in  Fig.  168, 
which  he  has  called  a  "  vacuum  augmenter,"  by  which  he  is  enabled 


348     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

to  obtain  the  vacuum  named,  27 J  to  28  inches,  without  any  other 
alteration  to  the  plant,  or  higher  vacua  with  the  increase  of  cir- 
culating water,  etc.,  mentioned.  The  apparatus  is  an  ingenious 
application  of  the  injector  principle,  applied  to  draw  off  the  air  and 
vapour  from  the  lower  portion  of  the  condenser  into  an  auxiliary 
condenser,  marked  in  the  drawing,  "augmenter  condenser."  The 
auxiliary  condenser  has  from  2  to  3  per  cent,  of  the  cooling  surface 
of  the  main  condenser,  and  its  office  is  to  cool  the  air,  and  partially 
condense  the  vapour  it  draws  off  before  it  enters  the  air  pump.  It 
will  be  remembered  that  the  lower  the  temperature  of  any  quantity 
of  air  that  has  to  be  dealt  with,  the  smaller  its  volume,  and  therefore 
the  work  the  air  pump  has  to  do  is  lessened.  The  main  pipe  leading 
from  the  condenser  to  the  air  pump,  is  shown  leaving  the  right  of 
the  condenser  in  the  drawing,  and,  as  will  be  seen,  the  auxiliary 
condenser  delivers  its  air  and  water  to  this  pipe  just  before  it  enters 
the  air  pump.  The  consumption  of  steam  in  the  steam  jet  is  stated 
not  to  exceed  1J  per  cent,  of  the  total  steam  dealt  with  at  normal 
load  in  the  main  condenser. 


Central  Condensing  Stations 

The  idea  of  distributing  power  by  means  of  electricity  from  one 
generating  station  has  led  to  the  idea  of  condensing  the  whole  of  the 
steam  from  a  group  of  engines  within  a  certain  range  by  one  con- 
densing plant,  the  same  reasoning  which  makes  the  central  generating 
plant  economical  also  making  the  central  condensing  plant  economical, 
providing  that  the  arrangements  are  properly  carried  out.  A  central 
generating  plant  is  rendered  economical  from  the  fact  that  a  smaller 
plant  can  be  employed  to  furnish  power  for  a  given  number  of 
machines  or  works  than  would  be  necessary  in  the  aggregate  if  each 
works  or  each  machine  was  provided  with  its  own  plant.  In  any 
works,  or  in  any  group  of  works,  there  are  always  some  machines 
which  are  temporarily  idle  from  various  causes.  If  we  take  a  fitting 
shop,  for  instance,  containing  lathes,  planing  machines,  drilling 
machines,  and  so  on,  it  is  very  rarely  that  the  work  any  one  machine 
is  doing  commences  and  ends  at  the  same  time  as  that  of  all  the 
other  machines.  The  work  is  necessarily  variable,  the  men  attending 
the  machines  are  variable,  and  the  times  of  stopping  and  starting 
machines  to  put  in  new  work,  or  to  attend  to  the  machine  for  one 
of  the  numerous  causes  from  which  it  requires  it,  necessarily  varies, 
and  hence  it  follows  that  approximately  not  more  than  40  per  cent, 
of  the  machines  are  working  at  any  one  time.  If,  again,  we  take  a 
group  of  engines,  say,  at  a  colliery,  a  steel  works,  or  some  works  of 
the  kind,  consisting  of  winding  engines,  hauling  engines,  pumps, 


CONDENSING   PLANT  349 

rail-mill  engines,  blowing  engines,  and  so  on,  it  will  be  found  that 
some  of  the  engines  are  always  stopped.  Thus,  winding  takes  place 
at  certain  intervals,  the  cage  requiring  to  be  unloaded  and  reloaded 
while  the  engine  stops ;  hauling,  though  it  is  less  liable  to  stop  on 
the  endless  rope  system  than  on  some  others,  is  still  liable  to  it; 
rail  mills  can  only  run  when  the  billets  are  ready  for  them,  and  so 
on,  and  it  follows  that  as  these  engines  are  working  more  or  less 
intermittently,  the  steam  which  they  exhaust  is  also  delivered  inter- 
mittently, and  the  total  quantity  of  steam  to  be  condensed  is  con- 
siderably less,  and  can  be  dealt  with  by  a  condensing  plant  of 
smaller  capacity  than  would  be  necessary  if  each  engine  had  its 
own  condenser.  There  is  the  objection,  of  course,  that  anything 
which  upsets  the  working  of  the  central  condensing  plant,  upsets 
the  working  of  the  engine ;  but  this  is  not  really  serious,  as  it  should 
always  be  arranged  that  the  exhaust  can  be  turned  on  to  the 
atmosphere  temporarily  and  quickly  in  case  of  accident.  A  central 
condensing  plant  has  been  fixed  by  the  Mirrlees  Watson  Company 
for  the  Scottish  Co-operative  Society,  and  arranged  for  condensing 
the  steam  from  three  sets  of  engines,  each  of  530  H.P.,  and  one 
of  330  H.P.,  all  of  the  high-speed  type,  the  steam  being  supplied 
by  four  water-tube  boilers  working  at  150  Ibs.  pressure  per  square 
inch.  The  plant  is  of  the  barometric  jet  condenser  type,  the  steam 
being  delivered  from  the  exhaust  of  all  the  engines  to  one  large  pipe, 
which  is  carried  vertically  up  to  the  condenser.  The  water  pumps 
and  the  air  pumps  stand  side  by  side  at  the  bottom,  and  the  cooling 
tower  at  the  top.  The  injection  water  is  pumped  to  the  condenser, 
and  passes  from  the  condenser  down  to  the  hot  well  in  the  usual 
way,  the  air  being  pumped  out  of  the  top  of  the  condenser  by  the 
air  pump,  and  being  cooled  and  separated  from  the  water  on  its  way 
by  passing  through  an  air  cooler  and  water  separator.  The  condenser 
is  of  the  type  described  on  p.  341,  fitted  with  trays  for  breaking  up 
the  water. 

Fig.  169  shows  a  central  condensing  plant  fixed  by  the  Klein 
Engineering  Co.,  in  which  open-surface  condensers  are  employed 
with  cooling  towers. 


The  Quantity  of  Cooling  Water  Required  for 

Condensing 

The  quantity  of  cooling  water  required  for  condensing  steam 
varies  with  the  form  of  condenser,  and  with  the  initial  temperature 
of  the  cooling  water,  the  velocity  at  which  the  water  is  passed 
through  the  condenser,  and  the  cooling  surface  exposed  in  the 


350    STEAM   BOILERS,  ENGINES,  AND  TURBINES 


FIG.  169. — Plan  and  Vertical  Section  of  Central  Condensing  Plant,  with  Cooling 
Tower,  made  by  the  Klein  Engineering  Co,  The  Condensers  are  of  the  open 
surface  type  described  on  page  339. 


CONDENSING  PLANT  351 

condenser.  It  has  been  explained  in  Chapter  I.  that  water  will 
absorb  heat  from  any  heated  surface,  directly  in  proportion  to  the 
difference  of  temperature  between  the  water  and  the  surface  it  is 
in  contact  with,  and  therefore  it  will  easily  be  understood  that  the 
lower  the  initial  temperature  of  the  water,  the  larger  capacity  it  has 
for  absorbing  heat  under  all  conditions.  It  will  be  understood  also 
that  in  the  surface  condenser,  the  tubes  through  which  the  water 
passes  are  virtually  heating  surfaces  for  the  water,  just  as  the  tubes 
in  a  water-tube  boiler  are.  It  will  be  understood,  also,  that  the 
quantity  of  heat  that  any  body  of  water,  say  a  gallon,  can  abstract 
from  the  steam  it  is  to  cool,  will  depend  directly  upon  the  difference 
between  the  initial  and  final  temperatures,  and  here  comes  in  a 
difference  between  the  injector  and  surface  condensers.  With  the 
surface  condenser  the  temperature  of  the  cooling  water  cannot 
possibly  leave  the  condenser  at  the  same  temperature  as  the  steam. 
In  practice  there  is  a  difference  of  from  15°  to  20°  F.  between  the 
two,  while  with  the  jet  condenser  the  water  is  raised  to  the  tempera- 
ture of  the  steam  itself,  providing  the  water  is  in  the  proper  pro- 
portion. Hence  it  is  claimed  that  the  jet  condenser  has  an  advantage 
over  the  surface  condenser  under  any  given  conditions  of  about 
fifteen  times  the  weight  of  steam.  That  is  to  say,  with  surface  con- 
densers the  cooling  water  required  is  in  the  neighbourhood  of  forty 
times  the  weight  of  steam  it  is  to  condense,  whilst  with  the  jet 
condenser  it  need  only  be  twenty-five  times.  With  either  form  of 
condenser,  however,  and  knowing  the  initial  temperature  of  the 
cooling  water,  and  the  temperature  to  which  it  can  be  raised  in  its 
passage  through  the  condenser,  the  calculation  for  the  quantity  of 
water  per  pound  of  steam  is  a  very  simple  one,  and  is  found  from 
the  following  formula  — 


where  Q  is  the  number  of  pounds  of  water  required,  S  is  the  number 
of  pounds  of  steam  to  be  condensed,  L  is  the  latent  heat  of  steam  at 
the  condenser  pressure,  T  being  the  initial  and  the  final  temperature 
of  the  cooling  water  ;  or  if  the  quantity  is  required  in  gallons,  the 
formula  becomes  — 

n      S  x  L  x  10 

Q=        T-* 

When  high  vacua  are  to  be  obtained,  the  conditions  are  more  severe 
than  with  low  vacua.  Above  a  vacuum  of  26  inches  the  latent  heat  of 
the  steam  is  increased,  as  will  be  remembered,  and  in  addition,  the 
volume  of  the  steam  is  also  very  largely  increased.  Thus,  approxi- 
mately, the  steam  doubles  its  volume  between  vacuum  of  26  and  28 


352    STEAM  BOILERS,  ENGINES,   AND   TURBINES 

inches,  and  again  more  than  doubles  it  between  28  and  29  inches.  The 
result  of  this  is,  as  explained  in  connection  with  the  Parsons  vacuum 
augmenter,  the  quantity  of  cooling  water  is  considerably  increased. 
Mr.  Parsons  found  that,  with  a  condenser  having  an  allowance  of  1 
square  foot  of  surface  per  indicated  H.P.,  a  vacuum  of  26  to  27  inches 
could  be  obtained  by  the  circulation  of  a  quantity  of  cooling  water  30 
times  that  of  the  steam  to  be  cooled,  the  initial  temperature  of  the  cool- 
ing water  being  70°  F.  For  higher  vacua  he  found  that  it  was  necessary 
to  increase  the  condenser  surface  to  1|  square  feet  per  indicated  H.P., 
and  to  increase  the  velocity  of  the  cooling  water  from  the  tubes,  to 
from  4  to  7  feet  per  second.  He  also  found  that  it  was  necessary 
to  construct  the  condenser  with  the  tubes  spaced  wider  apart  than 
is  usual,  so  that  the  steam  could  have  an  easy  flow  among  them,  and 
to  submerge  the  lower  tubes  in  the  condensed  water,  before  the  water 
was  carried  off  by  the  air  pump,  this  being  done  by  providing  a  weir 
at  the  bottom  of  the  condenser,  which  held  up  the  condensed  water, 
so  as  to  cover  two  or  three  rows  of  tubes.  It  should  be  mentioned 
that  this  arrangement  has  been  frequently  adopted  by  other  makers. 

It  should  be  mentioned  also  that  the  velocity  at  which  the 
cooling  water  passes  through  a  surface  condenser  has  an  important 
bearing  upon  its  cooling  effect,  up  to  a  certain  critical  figure.  Appa- 
rently there  is  a  certain  minimum  time  for  the  cooling  water  to  be  in 
contact  with  the  condenser  tubes,  in  order  that  it  may  absorb  the 
fullest  amount  of  heat  from  them,  and  this  forms  the  critical  speed. 
A  speed  which  does  not  allow  of  this  minimum  time  in  contact, 
should  not  give  as  high  a  cooling  effect  with  any  given  surface,  and 
with  any  given  difference  of  temperature  between  the  inlet  and  out- 
let of  the  cooling  water,  as  should  be  obtained  if  the  proper  minimum 
time  is  allowed.  This  would  be  the  case  of  too  high  a  velocity.  On 
the  other  hand,  up  to  the  critical  velocity,  the  water  does  no  good  by 
remaining  in  contact  with  the  heating  surface  longer  than  is  necessary 
for  it  to  abstract  the  maximum  amount  of  heat. 


Mr.  Richard  Allen's  Experiments  on  Condensers 

Mr.  Eichard  Allen,  of  the  firm  of  W.  H.  Allen  &  Son,  who  have 
made  a  speciality  of  surf  ace- condensing  plants  for  some  time,  carried 
out  some  experiments  upon  surface  condensers  a  couple  of  years  ago, 
which  are  exceedingly  interesting,  and  which  throw  a  very  important 
light  upon  the  question  of  the  quantity  of  cooling  water  required  under 
different  conditions,  and  with  different  vacua.  The  curves  shown 
in  Figs.  170  to  177  which  are  taken  from  the  paper  contributed  by 
Mr.  Allen  to  the  Institution  of  Civil  Engineers,  and  the  extracts  from 
his  paper,  are  reproduced  with  the  permission  of  the  Institution  and 


PLATE  26A.— Two-stage  Horizontal  Steam-driven  Slide-valve  Dry -air  Pump,  by  the  Mirrlees 
Watson  Co.,  specially  designed  for  high  vacua. 


LATE  26B.  —  Two-throw  Steam- 
driven  Slide-valve  Dry-air  Pumps, 
made  by  Mirrlees  Watson  Co.  The 
Air  Pumps  are  seen  above  the 
Steam  Cylinders. 


PLATE  26c.— Three-throw  Edwards'  Air  Pump, 
Electrically  Driven,  with  single  acting  Hot- 
well  Pump,  shown  on  the  left,  driven  from 
the  Air-pump  Shaft.  [To  face  p.  352. 


CONDENSING  PLANT 


353 


of  the  author.     The  first  set  of  curves  also  throw  a  very  interesting 
light  upon  the  steam  consumption  and  of  coal  consumption,  with  one 


STEAM-CONSUMPTION  OF 
CO  NO  EN  SING-PLANT  ENGINE 


8 

7 
CL 
X    6 

5 

4 

3 

SO 


I.HR  OFCONOENSING*-PLANT  ENGINE 


CIRCULATING  WATER  PER  LB 
OF  STEAM    CONDENSED 


VACUUM:     INCHES    OF    MERCURY 


ZS  INS. 


FIG.  170.— Curves  showing  Steam  and  Coal  Consumption,  etc.,  from  5"  to  25 
Vacuum,  with  one  engine  working,  in  Mr.  Richard  Allen's  experiments.    (Irans. 
Inst.  C.E.) 

engine  working  with  increasing  vacuum,  from  5  up  to  25  inches.     In 
Fig.  170  is  given  the  steam  consumption  per  K.W.  hour,  and  per 

2  A 


354    STEAM   BOILERS,  ENGINES,   AND  TURBINES 

electrical  H.P.  hour,  also  the  coal  consumption  per  K.W.  hour,  witl 
the  engine  employed  on  the  tests,  and  with  vacua  from  5  up  to  2c 


20 


NIP.  OF  AIR-PUMP  DISCHAfiGI 

==i^m 

TEMP.  OF  FEED -WATER 


CIRCULATING  WATER  PER  La 
OF  STEAM    CONDENSED 


5  10  IS  20 

VACUUM:     INCHES    OF    MERCURY 


25  INS. 


FIG.  171. — Curves  showing  Steam  and  Coal  Consumption,  etc.,  in  Mr.  Kichard 
Allen's  experiments,  with  Vacua  varying  from  5"  to  25",  and  with  two  Engines 
running.  (Trans.  Inst.  C.E.) 

inches.     It  will  he  noticed  that  both  the  steam  and  coal  consumption 
steadily  decrease,  as  shown  by  the  inclination  of  the  curve,  which  is 


CONDENSING  PLANT 


355 


practically  a  straight  liiie  in  the  three  cases,  as  the  vacuum  increases, 
and  Mr.  Allen  draws  the  conclusion  from  it,  that  while  it  is  probable 
that  if  condensing  with  high-speed  reciprocating  engines  were  carried 
to  a  higher  vacuum,  further  economies  would  result,  but  that  as  this 
would  mean  increase  in  size  of  engines,  increased  loss  by  radiation, 
and  so  on,  he  is  of  opinion  that  a  vacuum  of  25  to  26  inches  of  mercury 


GENERATORS  &  CONDENSING-PLANT 


CONSUMPTION  OF  CONDENSING- 
7  PLANT  AS  PERCENTAGE  OF  TOTAL 


I  HP  OF  CONDENSING-PLANT  AS 

PERCENTAGE  OF  TOTAL  I.  HP 

OF    GENERATORS 


IS 

COAL  SAVED  WITH   VARYING 
.20   VACUA,AS  COMPARED   WITH 
NON-CONDENSING 


VACUUM       INCHES 


IS  2O 

OF    MERCURY 


FIG.  172.— Curves  showing  Coal  saved,  and  consumption  of  Steam  and  Condensing 
Plant  in  Mr.  Richard  Allen's  experiments  with  two  Engines  working.  (Trans. 
Inst.  C.E.) 

is  about  the  economic  limit.  This  is  the  conclusion  that  practically 
the  whole  of  the  engineering  world  who  are  engaged  in  the  manu- 
facture of  reciprocating  engines  have  come  to.  In  Fig.  170  is  also  given 
the  quantity  of  circulating  water  per  pound  of  steam  condensed,  from 
5  up  to  25  inches  vacuum,  and,  as  will  be  seen,  it  increases  from  about 
11  Ibs.  at  5  inches  up  to  45  Ibs.  at  25  inches. 


Fig.  171  shows  curves 


356    STEAM  BOILERS,  ENGINES,  AND  TURBINES 

for  the  steam  consumption  per  K.W.  hour,  and  per  E.H.P.,  and  the 
coal  consumption  per  K.W.  hour,  with  two  engines  working,  and 
with  vacua  from  5  to  25  inches  of  mercury.  It  will  be  noticed  that 
the  decrease  in  steam  and  coal  consumption  is  more  marked  with  the 
two  engines  than  with  the  one.  Fig.  171  gives  the  circulating  watei 
per  pound  of  steam  condensed  with  the  two  engines  working,  and  it 
will  be  seen  that  the  result  is  rather  more  favourable  than  with  a 
single  engine.  Fig.  172  shows  the  indicated  H.P.  of  condensing  plant, 
and  the  consumption  of  steam  by  the  condensing  plant,  with  varying 
vacua,  as  percentages  of  the  total  steam  and  total  power  supplied  tc 
the  test  engines,  which  were  employed  in  driving  electricity  generators 
and  the  percentage  of  coal  saved,  with  varying  vacua,  as  compared 
with  the  coal  that  would  be  consumed  when  not  condensing.  It  will 
be  seen  that  the  consumption  of  steam  by  the  condensing  plant 
increases  from  4  per  cent,  with  5  inches  of  vacuum,  to  7i  per  cent 
with  25  inches,  while  the  indicated  H.P.  taken  by  the  condensing 
plant,  increases  from  about  If  per  cent,  to  nearly  3  per  cent.,  the 
coal  saved  being  10  per  cent,  with  5  inches  of  vacuum,  and  about  21 
per  cent,  with  25  inches  of  vacuum. 

It  will  be  understood,  of  course,  that  these  economies  apply  tc 
the  special  apparatus  under  test,  which  consisted  of  two  compound 
engines,  12-  and  21 -inch  cylinders  by  9-inch  stroke,  driving  electricity 
generators  of  165  and  137*5  K.W.,  but  the  author  believes  the  tests 
to  be  fairly  representative.  Fig.  173  shows  the  variation  in  the 
quantity  of  cooling  water,  with  its  initial  temperature  for  the  different 
vacua  shown. 

Mr.  Allen  estimates  that  for  vacua  of  25  to  26  inches,  with  the 
barometer  at  30  inches,  the  tube  surface  in  the  condenser  for  circula- 
ting water  having  a  temperature  not  exceeding  65°  F.  at  inlet,  should 
be  from  J  to  -^  square  foot  per  pound  of  steam  condensed,  and  witli 
circulating  water  at  higher  temperature,  from  J  to  I  square  foot  pei 
pound  of  steam.  It  will  be  noticed  that  these  figures  agree  practically 
with  those  given  by  Mr.  Parsons.  Further,  Mr.  Allen  estimates  that 
for  the  vacuum  mentioned  the  volumetric  capacity  of  the  air  purnps 
measured  by  the  number  of  cubic  feet  displaced  by  the  piston,  should 
not  be  less  than  0*6  cubic  foot  per  pound  of  steam  handled. 

Mr.  Allen  also  carried  out  a  further  series  of  tests,  with  the  objecl 
of  estimating  the  cooling  water  required  to  obtain  higher  vacua,  witl: 
different  initial  temperatures,  and  with  different  condenser  surfaces 
The  tests  were  carried  out  on  the  same  condenser,  different  quantities 
of  steam  being  passed  through  the  condenser  in  the  same  time,  to  vary 
the  quantity  dealt  with  per  square  foot.  Thus  1500  Ibs.  of  steam  pei 
hour  were  passed  through,  giving  5  Ibs.  of  steam  per  square  foot  oj 
tube  surface,  2000  Ibs.  per  hour,  2500  Ibs.  per  hour,  and  3000  Ibs.  pe] 
hour,  the  quantity  of  steam  dealt  with  per  square  foot  of  tube  surface 


CONDENSING  PLANT 


357 


CURVE 

READING  FOR  VACUUM 
EFF  CIENCY  AS  BELQW 


go* 71 56* 

TEMPERATURE  OF  CIRCULATING   WATER-SUPPLY 


FIG  173  —Curves  showing  the  quantities  of  Circulating  Water,  with  different  Vacua, 
and  different  Initial  Temperatures,  in  Mr.  Ricbard  Allen's  experiments.  (Trans. 
Inst.  C.E.) 


358     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

being  in  proportion  to  these  figures.  The  curves  given  in  Figs.  174  and 
175,  176  and  177  show  the  quantities  of  circulating  water  at  initial 
temperatures  of  65°,  70°,  75°,  80°  and  85°  F.,  and  with  vacua  ranging 
from  26^  inches  up  to  about  28'6  inches  of  mercury.  It  will  be 
noticed  in  Fig.  174,  in  which  5  Ibs.  of  steam  was  dealt  with  by  each 
square  foot  of  cooling  surface,  that  the  quantity  of  cooling  water  with 
an  initial  temperature  of  65°  F.  increases  from  35  Ibs.  per  pound  of 
steam  condensed  with  26J  inches  vacuum,  to  70  Ibs.  with  about 


1500  LBS.  OF  STEAM  PER  HOUR 

5  LBS. OF  STEAM  PER  SQ.FT.QF  COOLING-SURFACE 


50 


60  70  60  80  100 

POUNDS  OF  WATER  PER  POUND  OF  STEAM  CONDENSED 


(10 


120  LBS 


2000  LBS. OF  STEAM  PER  HOUR 

666  LBS  OF  STEAM  PER  SO.FT.OF  COOUNO-SURFACE 


50 


€0  7O  80  30  100 

POUNDS  OF  WATER  PER  POUND  OF  STEAM  CONDENSED 


110 


120  LBS 


FIGS.  174  and  175. — Curves  showing  the  different  quantities  of  Circulating  Water,  with  different 
Initial  Temperatures  and  different  Vacua,  in  Mr.  Richard  Allen's  experiments.^  (Trans.  Inst.  C.E.) 

28j  inches,  to  95  Ibs.  with  28^  inches,  and  to  120  Ibs.  with  about 
2 8 '7  inches.  With  water  at  70°  F.  initial  temperature,  the  quantity 
rises  from  35  Ibs.  with  26J  inches  vacuum,  to  120  Ibs.  with  about  28*4 
inches  vacuum,  no  higher  vacuum  apparently  being  obtainable  with 
the  water  available  at  that  temperature.  With  smaller  proportion  of 
cooling  surface,  or  what  amounts  to  the  same  thing,  larger  quantities 
of  steam  dealt  with  per  square  foot  of  cooling  surface,  the  results  are 
very  accentuated,  and  again  the  results  are  more  accentuated  with 


CONDENSING   PLANT 


359 


cooling  water  of  higher  initial  temperatures.  Thus  with  10  Ibs.  of 
steam  per  square  foot  of  cooling  surface,  the  quantity  of  cooling  water 
with  an  initial  temperature  of  65°  F.  is  about  37  Ibs.,  and  it  increases 
to  70  Ibs.  with  28  inches  vacuum,  and  to  120  Ibs.  with  28'3  inches, 
which  is  the  highest  vacuum  apparently  obtainable.  With  water 
having  an  initial  temperature  of  85  F.,  64  Ibs.  about  are  required  for 
26i  inches  vacuum,  and  78  Ibs.  with  27  inches,  120  Ibs.  with  27.3 
inches,  the  highest  obtainable.  These  figures  appear  to  the  author 


2500  IBS. OP  STEAM  PER  HOUR 

8  33  LBS  OF  STEAM  PER  SQ.FT. OF COOUNG-SURFACE 


GO  70  8O  9O  IOO 

POUNDS  OF  WATER   PER  POUND  OF  STEAM  CONDENSED 


3000  LBS.OF STEAM  PER  HOUR 

10  LBS  OF  STEAM  PER  SQ  FT  OF  COOLING-SURFACE 


6O  7O  8O  9O 

POUNDS  OF  WATER  PER  POUND  OF  STEAM   CONDENSED 


FIGS  176  and  177.— Curves  similar  to  Figs.  174  and  175,  but  with  smaller  Tube  surface  per  pound 
of  Steam  condensed.     (Trans.  Inst.  C.E.) 

to  be  very  striking  and  very  instructive,  because  it  must  not  be  for- 
crotten  that  in  addition  to  the  quantity  of  water  that  must  be  pro- 
vided, for  the  higher  vacua,  and  with  the  higher  temperature,  .and  the 
cost  of  providing  the  water,  as  apart  from  the  cost  of  driving  it 
through  the  condenser,  the  charges  for  pumping  will  increase  very 
rapidly  with  the  larger  quantities.  It  will  be  remembered  that  with 
a  Driven,  set  of  tubes  the  frictional  charge  for  driving  the  water 
through  them,  increases  as  the  square  of  the  velocity,  wjpch  means, 


360    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

of  course,  that  the  frictional  charge  will  increase  with  the  square  of 
the  quantity  of  water  passing  through  the  condenser  in  a  given  time.1 

Prof.   Weighton's   Experiments  on  Condensers 

Professor  K.  L.  Weighton,  of  the  Armstrong  College,  Newcastle-on- 
Tyne,  has  carried  out  a  very  interesting  series  of  experiments  in  the 
engineering  department  of  the  Armstrong  College,  designed  primarily 
to  compare  the  efficiency  of  the  Contraflo  condenser  with  the  ordinary 
form  of  surface  condensers.  Incidentally,  however,  the  experiments, 
which  are  very  much  on  the  lines  of  those  carried  out  by  Mr. 
Kichard  Allen,  throw  a  very  important  light  upon  the  question  of  the 
efficiency  of  surface  condensers  generally,  and  upon  the  quantity  of 
water  required,  with  varying  initial  temperatures,  varying  final  tem- 
peratures, and  varying  vacua.  In  addition  to  comparing  the  old  form 
of  condenser  with  the  Contraflo,  Professor  Weighton  carried  out  some 
experiments  upon  the  Contraflo  condenser,  with  solid  wooden  cores  of 
triangular  section  inserted  in  the  condenser  tubes.  The  condenser 
tubes  were  of  the  usual  form,  |-  inch  external  diameter  by  4  feet  long, 
the  tubes  being  1-J  inches  apart  from  centre  to  centre,  in  the  Con- 
traflo form,  and  1  ^  inches  in  the  old  form.  The  wooden  cores  were 
about  2  inches  longer  than  the  tubes,  and  were  merely  inserted  in  the 
tubes  without  any  fastening  whatever.  The  effect  of  the  wooden  core 
was  to  reduce  the  available  space  for  the  passage  of  the  water  in  the 
tubes,  and  therefore  to  reduce  the  quantity  of  water  passing  under 
any  given  pressure.  It  will  be  noted  that  this  experiment  is  on  the 
lines  of  what  has  been  mentioned  in  several  parts  of  this  book,  as 
the  ideal  condition  for  the  transmission  of  heat  from  one  fluid  to 
another,  when  the  two  fluids  are  separated  by  a  metal  diaphragm, 
the  ideal  condition  being  that  a  thin  stream  of  each  fluid  shall  pass 
on  opposite  sides  of  the  diaphragm  in  opposite  directions.  The  effect, 
however,  of  the  cores  inserted  in  the  tubes  was,  in  addition  to 
decreasing  the  available  space  for  the  passage  of  the  water,  to 
increase  somewhat  considerably — to  nearly  double  in  fact — the  fric- 
tional charge  for  the  passage  of  the  water  through  the  tubes.  It  will 
be  remembered  that  the  frictional  charge  depends  directly  upon  the 
extent  of  the  surface  over  which  the  water  runs,  and  it  will  be  seen 
that  this  surface  is  increased  by  the  three  sides  of  the  equilateral 
triangle  formed  by  the  cores.  It  appears  to  the  author  that  the  results 
obtained  by  Professor  Weighton  point  to  a  different  form  of  tube, 
viz.  one  having  the  same  area  as  the  reduced  area  in  the  tubes,  but 
without  the  increased  surface,  and  that  this  might  be  obtained  by 
either  an  elliptical  or  plainly  flat  tube.  There  are,  of  course, 

1  Mr.  Allen  informs  the  author  that  since  the  above  experiments  were  made,  his 
firm  have  suqpeeded  in  reducing  the  o[uantitv  of  circulating  water  for  high  vacua, 


(  CONDENSING   PLANT  361 

constructional  difficulties  in  the  way  of  adopting  a  form  of  tube  of  this 
kind,  but  it  appears  to  the  author  that  something  of  the  kind  might 
be  tried.  Professor  Weighton  found  that  the  temperatures  of  the  water 
in  the  hot  well,  for  all  degrees  of  vacua  exceeding  26  inches,  were 
from  10°  to  15°  lower  with  the  old  type  of  condenser  than  with  the 
Contraflo,  and  he  points  out  that  there  is  no  advantage  in  having  the 
temperature  of  the  water  in  the  hot  well  lower  than  is  necessary, 
that,  in  fact,  the  lower  the  temperature,  the  lower  is  the  efficiency  of 
the  steam  system  as  a  whole ;  because  if  the  water  from  the  con- 
denser has  to  be  used  for  boiler  feed,  every  degree  of  lower  tempera- 
ture has  to  be  made  up  at  the  expense  of  a  heating  from  the  boiler 
furnace.  Professor  Weighton  found  that  an  air  pump  capacity  of 
0'7  cubic  feet  per  pound  of  steam  condensed  was  as  large  as  was  neces- 
sary, providing  that  the  leakage  of  air  into  the  condensing  system 
was  prevented.  On  the  other  hand,  he  found  that  with  air  leakage, 
the  air  pump  power  required  was  increased  very  rapidly.  He  also 
found  by  using  a  dry  air  pump,  a  considerable  economy  of  condensing 
water  was  obtained,  but  at  the  cost  of  increased  pump  capacity.  He 
sums  up  the  conclusions  at  which  he  arrived  from  his  experiments 
as  follows  I— 

(1)  Efficiency    is    increased    in   a    surface    condenser    by    the 
removal  of  the  condensed  water  immediately  it  is  formed. 

(2)  Condenser  efficiency  is  obtained  with  a  minimum  condenser 
capacity  consistent  with  the  necessary  surface. 

(3)  Efficiency  is  obtained  by  fairly  high  speed  of  circulating  water. 

(4)  The  temperature  of  the  condensing  water  at  the   discharge 
may  be  equal  to,  or  slightly  higher  than  the  temperature  due  to  the 
vacuum. 

(5)  The   temperature  of   the  hot   well  may  be  from   3°  to  5° 
higher  than  the  temperature  due  to  the  vacuum. 

(6)  That  with  a  reasonably  air-tight  system,  an  air  pump  capacity 
of  0-7  cubic  feet  per  pound  of  steam  is  sufficient,  up  to  close  upon  29 
inches  vacuum. 

(7)  With  dry  air  pumps,  a  vacuum  of  28 £  inches  may  be  obtained 
at  a  condensation  rate  of  20  Ibs.  of  steam  per  square  foot  of  con- 
denser surface  per  hour,  and  with  24  times  the  quantity  of  cooling 
water  at  an  inlet  temperature  of  50°. 

(8)  With  dry  air  pumps,  a  condensation  rate  of  36  Ibs.  of  steam 
per  square  foot  of  condenser  surface  per  hour  can  be  obtained  with 
condensing   water   28    times   that  of  the   steam   condensed,  with  a 
vacuum  of  28 i  inches,  at  an  inlet  temperature  of  50°. 

Figs.  178  and  179  give  some  of  the  curves  obtained  by  Professor 
Weighton,  and  they  show,  as  explained  above,  the  effect  of  the  initial 
temperature  of  cooling  water,  the  speed  of  the  cooling  water,  and  the 
vacuum  obtained. 


362     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

It  will  be  noticed  that  Professor  Weighton  uses  cooling  water  of 
temperatures  from  45°  to  70°  F.,  while  Mr.  Eichard  Allen  used  cooling 


FIGS.  178.— Curves  showing  the  results  of  Prof.  Weighton's  experiments,  in  quantity 
of  Circulating  Water  required,  and  speed  of  the  Circulating  Water,  with  cores 
in  the  Condenser  Tubes.  (Trans.  Inst.  N.A.) 


FIG.  179. — Curves  showing  the  results  of  Prof.  Weighton's  experiments,  in  quantity 
of  Circulating  Water  required,  and  its  speed,  without  cores  in  Condenser  Tubes. 
(Trans.  Inst,  N.A.) 

water  of  temperatures  from  65°  to  85°.  Professor  Weighton's  curves 
showing  the  quantity  of  water  required  for  different  vacua  are  much 
steeper  in  the  early  portion  than  those  of  Mr.  Allen,  but  this  arises  from 


CONDENSING   PLANT  363 

the  fact  that  his  curves  commence  with  a  vacuum  of  22  inches,  while 
Mr.  Allen's  commence  with  26  J-  inches,  and  it  will  be  seen  that  the 
curves  are  of  practically  the  s*ame  form,  after  26 ^  inches,  though 
differing  in  position  on  the  diagram,  as  Mr  Allen's. 

With  No.  3  condenser,  with  which  the  greater  portion  of  the 
experiments  were  carried  out,  and  with  cores  in  the  tubes,  and  which 
apparently  was  best  suited  for  the  quantity  of  steam  delivered  by 
the  experimental  engine,  the  quantity  of  water  required,  with  an 
initial  temperature  of  45°,  rises  from  12  Ibs.  per  pound  of  steam  con- 
densed at  24  inches  vacuum,  to  15  Ibs.  at  27  inches,  to  18  Ibs.  at 
28  inches,  and  after  that  increases  very  rapidly,  as  the  vacuum  rises. 
The  effect  of  the  cores  in  the  tubes  is  fairly  marked,  as  will  be  seen 
from  the  different  curves. 

In  Fig.  180  Professor  Weighton  has  given  the  cost  in  circulating 
water  H.P.  of  the  attainment  of  given  vacuum,  under  different  con- 
ditions, from  which  it  will  be  seen  that  the  pump  H.P.  rises  very 
rapidly  after  28  inches  vacuum  is  reached. 

Fig.  181  gives  the  limit  beyond  which  the  power  absorbed  in 
pumping  exceeds  that  given  to  the  engine  by  the  higher  vacuum. 


Pumps  for  Condensers 

As  indicated  above,  two  pumps  are  required  for  nearly  every  form 
of  condenser,  one  to  supply  the  cooling  water,  and  the  other  to  remove 
the  condensed  products.  For  the  cooling  water  almost  any  form  of 
pump  may  be  employed,  a  favourite  form  being  the  centrifugal  pump, 
arranged  for  a  low  head,  which  may  be  driven  conveniently  by  an 
electric  motor,  or  a  high-speed  engine  of  any  convenient  form,  or 
again  by  a  belt  or  gearing  from  the  shaft  of  the  engine.  Plunger 
pumps  are  also  employed  for  the  circulating  water,  and  they  may  be 
of  single,  double,  or  triple  barrel,  and  driven  by  an  electric  motor,  or 
any  convenient  source  of  power  again.  As  the  quantity  of  circulating 
water  varies  with  the  load  that  is  on  the  engine  the  condenser  is 
working  with,  the  circulating  pump  should  be  capable  of  having  its 
speed  varied,  within  certain  limits,  unless  it  is  also  arranged  that  the 
engine  is  always  working  at  a  certain  proportion  of  its  full  power,  a 
condition  that  very  rarely  occurs.  Variation  of  speed  of  the  pump 
may  be  accomplished  in  the  case  of  the  electric  motor  by  varying  the 
excitation  of  the  field  magnets,  and  in  the  case  of  the  steam  engine 
by  varying  the  pressure  of  steam,  by  the  aid  of  the  stop  valve.  The 
quantity  of  water  may  also  be  varied  by  the  use  of  one  of  the  pumps 
with  variable  stroke,  on  the  market,  keeping  the  speed  of  the  pump 
itself  constant.  With  plunger  pumps  the  quantity  of  water  thrown 
by  each  plunger  can  be  varied  by  varying  the  length  of  the  stroke 


364    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


FIG.  180. — Curves  showing  the  cost  in  H.P.  in  circulating  the  Cooling  Water,  with 
varying  Vacua,  and  with  cores  in  Condenser  Tubes  and  without,  as  given  by 
Prof.  Weighton's  experiments.  (Trans.  Inst.  N.A.) 


»-£ 


r! 


tic.  181.— Curves  showing,  by  Prof.  Weighton's  experiments,  the  limit  beyond 
which  the  power  expended  in  pumping  the  Circulating  Water  exceeds  that 
conferred  by  the  higher  Vacuum.  (Trans.  Inst.  N.A.) 


CONDENSING  PLANT  365 

and  keeping  the  speed  constant,  or  by  varying  the  speed  keeping  the 
length  of  stroke  constant.  Up  till  recently  the  universal  method  was 
varying  the  speed,  but  with  the  advent  of  the  variable  stroke  pumps 
introduced  by  Messrs.  Mather  &  Platt  and  Hayward,  Tyler  &  Co.,  the 
speed  can  be  maintained  constant,  while  the  stroke  is  varied.  This 
arrangement  is  very  convenient  for  driving  with  electric  motors,  and 
it  is  also  convenient  for  driving  by  means  of  steam  engines,  as  it 
enables  the  self-governing  property  of  the  electric  motor  to  be  made 
use  of,  and  also  in  the  case  of  the  steam  engine,  enables  the  governor 
to  be  set  for  a  certain  speed,  and  allows  the  governor  to  take  charge 
of  the  engine.  Plate  24A  shows  the  condenser  of  a  set  of  large 
blowing  engines  at  a  steel  works ;  Plate  24B  a  large  double-acting 
horizontal  steam  pump  ;  25A  a  pair  of  Mirrlees  Watson  vertical  steam 
pumps  ;  2  SB  and  25o,  two  of  Hall's  vertical  steam  pumps ;  and  25c  a 
surface  condenser,  with  air  and  circulating  pumps. 


Air  Pumps 

The  air  pump  is  a  different  apparatus  to  the  circulating  pump. 
It  is  called  the  air  pump  because,  though  it  also  in  the  majority  of 
cases  removes  the  condensed  water  from  the  condenser,  the  volume  of 
air  which  comes  over  with  the  steam,  and  which  it  is  of  the  greatest 
importance  to  remove,  in  order  that  vacuum  may  be  obtained,  is  so 
much  greater  than  that  of  the  water. 

There  are  practically  two  forms  of  air  pumps,  one  designed  to 
remove  the  air  only,  and  the  other  designed  to  remove  the  air  and 
water,  the  two  forms  being  employed  in  the  cases  for  which  they  are 
adapted,  the  dry  air  pump  as  it  is  called  being  used  where  no  water  is 
present,  and  the  wet  air  pump  where  condensed  water  has  to  be 
removed  as  well  as  air. 

The  dry  air  pump,  the  pump  which  removes  air  only  from  the  con- 
densing plant,  is  really  an  air  compressor.  It  withdraws  air  from  the 
condenser  by  suction,  just  as  an  air  compressor  draws  air  from  the 
atmosphere  by  suction,  and  it  delivers  the  air  to  the  atmosphere  after 
compressing  it  to  a  certain  figure,  just  as  the  air  compressor  delivers 
the  compressed  air  to  a  receiver.  The  dry  air  pump  consists  of  a 
cylinder  with  a  piston,  and  driven  by  any  convenient  source  of  power, 
usually  its  own  engine.  The  dry  air  pump  is  often  worked  in  two 
stages,  very  much  as  air  compressors  are,  the  air  being  drawn  into  the 
first  stage  merely,  then  cooled,  and  ejected  in  the  second  stage. 
Forms  of  dry  air  pumps  are  shown  in  Plates  26 A  and  26B.  The 
value  of  the  arrangement  is  due  to  the  fact  that,  with  high  vacua, 
the  air  pump  has  to  force  the  condensed  products  out  against  the 
pressure  of  the  atmosphere,  and  the  work  is  more  easily  accomplished 


366    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

where  the  second  stage  shields  the  first,  and  where  the  volume  of  the 
air  and  incombustible  gases  is  reduced  by  cooling  before  being 
ejected. 

Bucket  Air   Pumps 

Edwards  Air  Pump.— In  the  Edwards  air  pump,  a  section  of 
which  is  shown  in  Fig.  182,  and  which  is  used  very  largely  for  con- 
densing purposes,  it  is 
claimed  that  the  arrange- 
ment has  been  very  much 
simplified  by  the  removal 
of  bucket  and  foot  valves 
that  were  employed  in  the 
earlier  forms  of  air  pumps. 
As  will  be  seen  from  the 
drawing,  the  moving  por- 
tion of  the  pump,  that 
which  corresponds  to  the 
piston  in  other  pumps,  is 
shaped  conically  in  the 
lower  part  and  cylindri- 
cally  above,  and  the  bottom 
of  the  pump  vessels  also 
conically  shaped  to  fit  the 
bucket.  The  bucket,  or 
piston,  moves  up  and 
down  in  the  central  barrel 
shown,  and  the  condensed 
water  and  air  flow  into 
the  bottom  of  the  pump 
chamber  through  the  aper- 
ture on  the  left,  \vhen  the 
bucket  is  off  the  bottom. 

As  the  bucket  descends,  it  forces  the  air  and  water  up  into  the  barrel 
above  th*e  bucket,  through  the  ports,  which  are  exposed,  immediately 
above  the  cylindrical  portion  of  the  bucket.  When  the  bucket  has 
completed  its  downward  stroke  and  has  expelled  all  the  water  in  the 
chamber  below,  having  forced  it  into  the  circular  chamber  above,  it 
commences  its  up  stroke,  closing  the  ports  through  which  the  water 
and  air  entered,  as  it  rises,  then  forcing  the  whole  of  it  upwards,  and 
discharging  them  through  the  valve  at  the  top  of  the  barrel.  It  will 
be  understood  that  the  problem  of  forcing  air  and  water  out  is  very 
much  more  difficult,  that  is  to  say,  it  requires  very  much  more 
accurate  working  between  the  pump  bucket  and  the  stationary  parts 


FIG.  182.— Section  of  Edwards  Air  Puinp,  showing 
the  Form  of  the  Piston. 


CONDENSING  PLANT  367 

of  the  pump  than  one  in  which  merely  water  is  to  be  handled.  If 
the  air  is  to  be  expelled,  the  pump  must  work  air-tight,  and  this  is 
what  is  claimed  for  the  Edwards  air  pump.  It  is  also  claimed  that 
the  Edwards  pump,  dealing  with  the  water  mechanically,  does  not 
depend  upon  the  pressure  in  the  condenser  to  drive  it  into  the  pump, 
and  secondly  an  increase  of  speed  does  not  impair  its  efficiency.  The 
question  of  the  elimination  of  back  pressure  in  the  engine  cylinders 
is  closely  bound  up  with  the  working  of  the  air  pump,  and  conse- 
quently it  is  claimed  that  the  Edwards  pump  accomplishes  this.  In 
the  Edwards  pump  the  speed  at  which  the  water  is  propelled  is 
necessarily  the  same  as  that  of  the  bucket  which  forces  it.  Plates 
26c,  27A  and  27s  show  forms  of  Edwards  air  pump  made  by 
Mirrlees  Watson,  and  Plate  27c  a  complete  standard  surface  con- 
densing plant,  with  air  and  circulating  pumps. 


Cooling  the  Circulating  Water  for  Condensers 

As  already  explained,  the  question  of  the  use  of  condensers  with 
steam  engines  is  one  of  relative  economy,  in  which  a  balance-sheet 
should  be  made  out.  On  the  one  hand,  by  condensing  the  exhaust 
steam,  a  certain  amount  of  coal  is  saved,  owing  to  the  lessening  of 
the  back  pressure  in  front  of  the  piston  on  its  return  stroke,  and  a 
further  saving  is  often  effected  by  utilizing  the  condensed  water, 
which  is  at  a  comparatively  high  temperature  for  feeding  the  boilers. 
On  the  other  hand,  as  explained,  condensers  require  circulating 
pumps  for  forcing  the  water  through  the  condensers,  whatever  the 
form  may  be,  unless  there  happens  to  be  a  supply  of  water  at  a  suffi- 
cient height  to  force  it  through  the  condenser,  a  thing  that  will  not 
often  happen.  In  nearly  every  form  of  condenser  also  an  air  pump  is 
necessary,  and  this  also  absorbs  a  certain  amount  of  power. 

With  an  abundant  supply  of  cheap  water,  the  economy  of  con- 
densing in  the  great  majority  of  cases  is  very  marked.  It  has  been 
estimated  that  the  saving  in  coal  and  water  by  condensation  ranges 
from  25  per  cent,  with  steam  at  150  Ibs.  pressure,  to  35  per  cent,  with 
70  Ibs.  pressure,  and  this  does  not  represent  the  whole  of  the  saving, 
as  less  steam  being  required,  owing  to  the  absence  of  back  pressure, 
smaller  boiler  plant  may  also  be  used,  effecting  a  saving  in  the  capital 
account.  Condensing  plant  is  also  estimated  to  take  from  1  to  7  per 
cent,  of  the  power  furnished  by  the  engine  to  drive  the  circulating 
and  air  pumps,  the  power  required  varying  with  the  conditions.  But 
all  of  this  economy  may  easily  be  neutralized  in  a  very  large  number 
of  cases  by  the  heavy  cost  of  circulating  water.  Towns  water  is 
always  too  expensive  for  economical  condensing.  Waterworks 
engineers  are  faced  with  greater  and  greater  demands  for  water  in  all 


368    STEAM  BOILERS,   ENGINES,   AND  TURBINES 

the  large  towns  for  the  ordinary  domestic  consumption,  and  are  being 
obliged  to  lay  out  more  and  more  ambitious  schemes  to  provide  it, 
and  they  do  not  want,  and  will  not  have  if  they  can  avoid  it,  any 
consumption,  especially  large  consumption,  such  as  would  rule  with 
condensing  plant,  outside  of  domestic  consumption.  Hence  charges 
for  water  from  towns  supply  are  always  prohibitive.  It  often  happens 
also  that  the  cost  of  pumping  from  a  river  which  is  at  a  distance,  or 
from  springs  at  a  distance,  is  considerable  and  in  those  cases  it  is 
often  an  open  question  whether  condensation  is  economical,  while  the 
condensing  plant  is  an  additional  apparatus  to  be  looked  after.  But 
the  trouble  can  usually  be  completely  overcome,  and  is  overcome  in  a 
great  number  of  instances,  by  the  adoption  of  cooling  apparatus  for 
the  circulating  water.  The  circulating  water  in  passing  through  the 
condenser  has  its  temperature  raised  20°  F.  and  upwards,  and  if  it 
can  be  reduced  again  to  the  initial  temperature,  or  by  a  substantial 


FIG.  183.— Diagram  showing  the  Course  of  the  Water  when  a  Cooling  Tower  is  used, 
in  connection  with  a  Condenser. 

number  of  degrees,  it  may  be  employed  over  and  over  again,  with 
a  small  loss  in  the  process  of  cooling;  with  proper  appliances,  the 
cost  of  the  cooling  water  then  being  the  cost  of  the  water  required 
to  make  up  the  loss  by  evaporation,  plus  the  interest  on  the  cooling 
plant  and  the  cost  of  running  it.  Fig.  183  shows  diagraminatically 
the  arrangement  of  a  condenser  and  a  cooling  tower.  The  diagram 
applies  to  any  form  of  cooling  appliance,  if  the  fan  is  omitted. 


Cooling  Ponds 

The  simplest  form  of  cooling  apparatus  is  that  which  is  employed 
so  largely  in  Lancashire,  in  connection  with  the  cotton  mills,  viz.  a 
pond  in  the  neighbourhood  of  the  engine  house,  into  which  the  cool- 
ing water  is  discharged  after  passing  through  the  condenser,  and  from 
which  the  circulating  pump  takes  its  suction.  It  has  been  estimated 
that  cooling  ponds  used  for  the  purpose  must  have  a  store  of  450 
gallons  per  indicated  H.P.  and  that  they  should  have  a  surface 


PLATE  27A. — Single-throw  Vertical 
Edwards'  Air  Pump,  by  Mirrlees 
Watson,  with  working  parts  being 
taken  out  for  inspection. 


PLATE  27s. — Three-throw  Vertical  Edwards'  Air 
Pump,  with  working  parts  exposed.  Made  by 
the  Mirrlees  Watson  Co. 


PLATE  27c. — Mirrlees  Watson  standard  arrangement  of  Surface  Condensing  Plant,  with 
Two-throw  Edwards'  Air  Pump  and  Centrifugal  Circulating  Pump,  the  two  Pumps 
driven  by  one  Electric  Motor,  as  shown.  [To  face  p.  368. 


CONDENSING   PLANT  369 

of  26  square  feet  per  indicated  H.P.  for  day  running  only,  and  52 
square  feet  for  day  and  night  running.  The  pond  or  reservoir 
should  be  divided  into  sections,  if  possible,  or  at  any  rate  it  should  be 
arranged  that  the  suction  water  for  the  condenser  shall  be  taken 
from  a  point  as  far  as  possible  from  that  at  which  the  heated  water 
from  the  condenser  is  delivered,  and  where  possible,  baffles  or  other 
obstructions  should  be  introduced  to  prevent  the  passage  of  the 
heated  water  directly  to  the  suction  pipe  of  the  circulating  pump. 

The  cooling  of  the  water  in  the  cooling  pond  is  effected  by  the 
evaporation  which  takes  place  from  the  surface  of  the  pond,  and  it 
will  be  greatest  in  hot  weather,  providing  that  the  atmosphere  is  not 
heavily  impregnated  with  moisture.  Evaporation  takes  place  from 
the  surface  of  any  body  of  water,  directly  in  proportion  to  the  surface 
of  the  water  exposed,  and  also  directly  in  proportion  to  the  difference 
of  tension  of  the  vapour  issuing  from  the  water,  and  that  already  present 
in  the  atmosphere.  When  the  atmosphere  contains  only  a  small 
proportionate  quantity  of  moisture,  the  tension  of  its  vapour  will  be 
comparatively  low,  and  evaporation  will  go  on  comparatively  freely, 
the  cooling  effect  being  approximately  10,000  heat  units  for  every 
gallon  of  water  evaporated.  In  the  muggy  weather  we  are  familiarwith, 
and  which  is  sometimes  common  in  summer,  the  mugginess  of  which  is 
due  to  the  saturation  of  the  atmosphere  with  moisture,  the  tension  of 
the  vapour  in  the  atmosphere  is  high,  and  it  may  be  so  high  in  com- 
parison to  that  of  the  vapour  emanating  from  the  surface  of  the  pond, 
that  no  evaporation  takes  place,  and  even  that  deposit  of  vapour  takes 
place  in  the  pond  from  the  atmosphere.  It  is  estimated  that  with  a 
good  reservoir  and  pipes,  one  gallon  of  water  per  indicated  H.P.  hour 
is  lost  by  evaporation  from  the  pond  while  the  engines  are  running. 


Cooling  Ponds  with  Nozzles 

An  extension  of  the  simple  cooling  pond  is  a  pond  in  which 
pipes  are  stretched  across,  slightly  above  the  surface  of  the  pond, 
usually  at  right  angles  to  each  other,  nozzles  being  placed  at 
intervals  above  the  pipes,  and  the  water  to  be  cooled  being  driven 
through  the  nozzles,  carried  up  a  certain  distance  into  the  atmo- 
sphere in  the  form  of  a  spray,  and  falling  down  to  the  surface 
of  the  water.  The  nozzles  may  give  a  simple  spreading  motion, 
similar  to  that  of  the  rose  of  a  watering-pot,  or  they  may  give  a 
whirling  motion  by  passage  through  a  nozzle  having  a  screw  section, 
theVwhirling  motion  being  claimed  to  give  an  increased  spreading  to 
the  spray,  as  it  issues  from  the  nozzle.  The  object  of  spraying  the 
water  is  to  break  it  up  and  to  expose  the  individual  particles,  as  far 
as  possible  to  the  action  of  the  air  in  the  neighbourhood.  Air  has  a 

2  B 


3/o    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

certain  capacity  for  moisture,  as  already '  explained,  but  it  can 
exercise  this  capacity,  and  can  abstract  moisture  only  from  the 
surface  of  any  body  of  water  with  which  it  is  in  contact.  Thus,  in 
the  case  of  a  pond,  evaporation  can  only  take  place  from  the  water 
on  the  surface,  while  when  the  water  is  formed  into  the  fine  spray, 
mentioned,  a  certain  amount  of  evaporation  may  take  place  from 
each  of  the  particles  into  which  it  is  broken  up,  provided  that  the 
air  in  the  neighbourhood  is  not  already  saturated.  It  will  be 
understood,  of  course,  that  evaporation  is  going  on  from  the  surface 
of  the  pond,  above  which  the  nozzles  project,  as  well  as  from  the 
spray  into  which  the  issuing  water  is  formed,  and  the  result  should 
be  that  a  smaller  pond  should  be  able  to  do  the  work. 

A  further  extension  of  the  pond  and  spraying  nozzle  method, 
which  is  sometimes  employed  is,  the  water  is  carried  in  pipes  to  a 
height  of  about  6  feet  above  the  surface  of  the  pond,  and  is  there 
sprayed,  and  allowed  to  fall  in  jets  on  to  the  surface  of  the  pond. 
One  of  the  objections  to  spraying  water  in  the  manner  described, 
which  applies  more  particularly  to  the  method  in  which  the  water  is 
carried  to  a  considerable  height  above  the  surface  of  the  pond,  is 
that  when  any  wind  is  blowing,  a  somewhat  serious  percentage  of  the 
water  is  carried  off  by  the  wind.  It  has  been  mentioned  that  the  air 
absorbs  moisture,  and  when  air  is  travelling,  as  when  a  wind  is 
blowing,  it  carries  the  moisture  it  absorbs  away  with  it.  The  moist 
south-west  winds  that  we  are  so  familiar  with  in  nearly  every  part 
of  these  islands,  are  striking  instances  of  this,  the  wind  having 
absorbed  moisture  from  the  sea  over  which  it  has  passed,  and 
delivering  it  to  the  earth  when  it  arrives.  The  difficulty  may  be 
overcome,  and  is  in  later  forms  of  cooling  apparatus,  arranged  upon 
these  lines,  by  enclosing  the  pond  by  a  system  of  louvre  boards, 
fixed  between  uprights,  and  so  arranged  that  they  can  be  opened  or 
closed  at  will.  Louvre  boards  are  similar  to  Venetian  blinds.  They 
consist  of  thin  boards,  held  between  uprights,  and  arranged  to  move 
from  a  horizontal  position,  when  air  passes  freely  between  them,  to 
the  position  in  which  they  lie  close  together,  like  slates  upon  a  roof, 
and  when  very  little  air  can  pass.  By  fixing  louvre  boards  all  round 
the  pond,  or  on  those  sides  against  which  the  prevailing  winds  blow, 
and  arranging  to  move  the  boards  as  required,  the  cooling  plant  can 
be  controlled,  and  the  loss  minimized. 


Cooling  Towers 

Another  method  of  cooling  the  circulating  water  is  by  the  aid  of 
what  are  termed  cooling  towers.  They  are  towers  of  various  forms, 
and  of  various  designs,  but  all  have  the  one  thing  in  common,  that 


CONDENSING    PLANT  371 

the  water  to  be  cooled  is  pumped,  either  to  the  top  of  the  tower,  or 
to  a  point  at  a  considerable  height  above  the  ground,  and  is  there 
allowed  to  find  its  way  down  to  the  surface  of  the  ground,  but  in 
doing  so  is  broken  up  into  as  fine  particles  as  possible,  and  during 
the  course  of  its  descent  is  exposed  to  a  current  of  air,  the  air 
absorbing  moisture  in  the  form  of  vapour  from  the  descending  water, 
the  heat  necessary  to  convert  the  water  into  vapour  being  taken 
largely  from  the  water  itself. 


Cooling  Towers  without  Vertical  Draught 

The  simplest  form  of  cooling  tower  is  that  in  which  the  action  of 
the  wind  is  depended  upon  entirely  for  the  evaporative  and  cooling 


Section 
Water  inlet 


Side  Elevation. 


Lfistribution  troughs 


Cooling  stacks 


Louvre  boards 


FIG.  184. — Cooling  Tower,  for  Wind  Draught,  made  by  Messrs.  Balcke  &  Co.  The 
Boards  over  which  the  Water  drips  are  shown  on  the  left  of  the  Figure,  the 
Louvre  Boards  on  the  right. 

effect.  In  this  form  of  tower  the  apparatus  for  breaking  up  the 
water  into  fine  drops,  descriptions  of  which  are  given  below,  is  built 
usually  on  top  of  a  building,  where  such  space  is  available,  in  a 
rectangular  form,  and  in  the  later  patterns  is  surrounded  by  walls  of 
louvre  boards,  as  explained  in  connection  with  cooling  ponds.  The 
louvre  boards  are  opened  and  closed,  according  to  the  force  of  the 
wind,  and  evaporation  takes  place  by  the  action  of  the  wind,  pass- 
ing through  the  laths,  etc.,  used  for  breaking  up  the  water  into 
fine  drops,  just  as  in  the  case  of  the  pond  with  spraying  appa- 
ratus. The  objection  to  this  form  of  apparatus  is  similar  to  that 
ruling  with  chimneys.  In  order  that  it  may  be  under  the  control  of 
the  engineer,  it  must  be  made  large  enough  to  cool  the  necessary 
quantity  of  water  for  condensing  purposes,  under  the  conditions  of 


372     STEAM   BOILERS,   ENGINES,   AND   TURBINES 

largest  power  service,  and  also  under  the  conditions  of  lowest  evapo- 
rating effect  in  the  atmosphere.  It  is  doubted  by  many  engineers, 
whether  the  additional  cost  rendered  necessary  to  meet  these  con- 
ditions, combined  with  the  comparative  uncertainty  of  the  control  of 
the  evaporative  effect,  especially  where  wind  is  frequently  changing, 
does  not  more  than  neutralize  the  additional  cost  of  other  plant. 
Fig.  184  shows  one  of  these  cooling  towers. 

In  the  more  frequent  arrangement  of  cooling  towers  a  draught  is 
provided,  carrying  the  air  through  the  body  of  the  tower,  very  much 
in  the  same  manner  as  a  draught  is  provided  for  a  boiler  furnace,  and, 
as  in  that  case,  there  are  two  methods  of  providing  the  draught.  It 
can  be  furnished  by  a  chimney,  or  by  fans.  Chimney  draught  is  less 
expensive  to  maintain,  and  also  usually  involves  a  smaller  capital 
outlay,  but  it  has  the  same  limitations  as  chimney  draught  for  boiler 
furnace.  It  is  not  possible  to  increase  the  draught,  if  it  should  be 
necessary  to  do  so,  beyond  the  capacity  of  the  chimney  to  furnish 
the  draught,  and  it  is  also  subject  to  the  further  drawback,  common 
with  the  furnace  chimney,  that  the  state  of  the  atmosphere  outside  of 
the  chimney,  will  change  the  draught  inside  the  chimney. 

Chimney  Cooling  Towers 

As  explained  above,  the  chimney  cooling  tower  provides  for  the 
passage  of  air  through  the  body  of  the  tower,  and  therefore  provides 
the  necessary  air  to  cause  evaporation  of  the  water  that  is  to  be 
cooled,  by  creating  a  difference  of  pressure  between  the  bottom  of 
the  tower  and  the  outlet  at  the  top  of  the  chimney,  and  this  differ- 
ence of  pressure  is  created  as  in  the  boiler  chimney,  by  the  difference 
in  weight  between  the  column  of  air  in  the  chimney,  plus  that  in 
the  body  of  the  tower  itself,  and  the  equivalent  column  of  air  outside 
of  the  chimney.  In  the  case  of  the  cooling  tower,  there  is  not  the 
high  temperature  available  that  exists  in  the  boiler  furnace,  and  it  is 
not  possible  to  produce  a  volume  of  hot  gases,  as  is  done  in  that  case, 
but  the  equivalent  is  obtained  by  the  air  which  has  passed  through 
the  body  of  the  tower,  and  which  has  come  in  contact  with  the  water 
that  is  being  cooled,  having  its  temperature  raised,  and  further,  by  a 
portion  of  the  volume  previously  occupied  by  the  air  being  now 
occupied  by  the  vapour  of  water.  It  was  explained  in  the  first 
chapter,  that  the  different  heights  at  which  the  barometer  stands,  and 
which  weather-wise  people  have  come  to  regard  as  indicating  fine  or 
wet  weather,  is  due  to  the  fact  that  when  moisture  is  present  in  the 
atmosphere,  it  displaces  an  equivalent  portion  of  air,  within  any 
given  space,  and  therefore  the  column  of  air  and  moisture  standing 
above  any  particular  point  on  the  surface  of  the  earth,  where  a 


CONDENSING   PLANT 


373 


barometer  may  be  fixed,  will  decrease  as  the  percentage  of  moisture 
it  contains,  increases,  and  as  the  percentage  of  moisture  increases,  the 
probability  of  rain  also  in- 
creases. The  same  thing  ap- 
plies to  the  cooling  tower,  the 
increased  quantity  of  moisture 
present  in  the  air  within  the 
tower,  causes  it  to  be  lighter 
than  the  equivalent  column 
of  air  outside  of  the  tower, 
and  this  creates  the  necessary 
difference  of  pressure  to  force 


Water  inlet 


FIG.  185.— Section  of  Chimney  Cool- 
ing Tower,  made  by  Messrs.  Balcke. 
The  Air  Current  is  in  the  opposite 
direction  to  the  Water  Current. 
The  Chimney  is  of  Wood. 


FIG.  186.— Barnard  Chimney  Cooling  Tower. 
The  Cooling  Appliances  consist  of  Galvan- 
ised Iron  Mats,  arranged  vertically,  and 
the  Chimney  is  of  Iron. 


the  air  through  the  tower.    The  difference  of  pressure  in  the  chimney 
cooling  tower  is   usually  not  great.      It  will  not  exceed   0'5  inch 


374    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

water  gauge,  because  the  resistance  offered  by  the  cooling  tower  is 
comparatively  small,  if  properly  designed.  A  frequent  arrangement 
with  chimney  cooling  towers  is— The  body  of  the  tower  where  the 
water  is  being  sprayed  is  comparatively  large,  it  is  spread  out  so 
as  to  cover  a  comparatively  large  area,  while  the  chimney  has  a 
smaller  area, 

Chimney  towers  vary  in  form,  but  are  built  on  very  much  the 


FIG.  187. — Another  form  of  Barnard  Chimney  Cooling  Tower.  The  Air  passes  up 
through  the  Centre  and  out  at  the  Sides,  the  Water  trickling  over  the  Mats, 
which  are  arranged  radially  round  the  Centre. 

same  lines.  The  tower  proper,  as  indicated  above,  in  which  the  appa- 
ratus is  held,  that  is  employed  to  spray  the  water,  occupies  the 
lower  part  of  the  tower,  being  carried  up  to  a  sufficient  height,  and 
occupying  a  sufficient  space  to  provide  for  treating  the  largest  quan- 
tity of  water  that  may  be  wanted  to  be  handled,  under  the  most 
severe  conditions  of  work.  Above  the  cooling  tower  proper  is  the 


CONDENSING  PLANT  375 

chimney,  and  the  water  to  be  cooled  is  led  into  the  cooling  tower  at 
the  base  of  the  chimney,  being  broken  up,  and  caused  to  trickle 
down  to  the  bottom,  as  already  explained.  At  the  bottom  of  the 
tower  are  entrances  for  the  air,  and  it  passes  up  through  the  spaces 
between  the  apparatus  employed  for  breaking  up  the  water,  and  at 
the  top  of  the  cooling  portion,  passes  into  the  chimney,  and  away  to 
the  atmosphere.  Fig.  185  shows  a  section  of  a  chimney  cooling 
tower  by  Messrs.  Balcke.  Tigs.  186  and  187  show  Barnard  chimney 
cooling  towers. 

It  will  be  evident  that  the  height  and  size  of  the  chimney  must 
be  such  that  under  the  very  worst  conditions,  both  of  working  and 
of  the  outside  atmosphere,  the  difference  of  pressure  created  between 
the  top  and  bottom  of  the  cooling  tower,  is  sufficient  to  cause  the 
necessary  quantity  of  air  to  pass  through  the  tower,  to  evaporate  the 
necessary  quantity  of  water.  It  should  be  mentioned  that  this  is 
one  of  the  difficulties  that  has  sometimes  arisen  in  connection  with 
the  use  of  cooling  towers.  The  engineer  who  has  been  responsible 
for  the  design  and  fixing  of  the  cooling  tower,  has  not  worked  as  he 
should  have  done,  to  the  worst  conditions  he  will  have  to  meet,  and 
consequently  in  muggy  weather,  for  instance,  when  the  outside 
atmosphere  is  comparatively  light,  the  draught  through  the  cooling 
tower  has  not  been  sufficient  to  cause  the  necessary  evaporation,  and 
the  cooling  water  has  not  been  sufficiently  lowered  in  temperature, 
the  vacuum  in  the  condenser  has  gone  back,  and  the  engines  have 
not  been  able  to  do  as  much  work  as  they  should  have  done. 


The  Cooling  Tower  with  Fan  Draught 

The  Cooling  tower  with  fan  draught  is  the  equivalent  of  the 
boiler  furnace  with  forced  draught.  The  tower  is  constructed  in  the 
usual  way,  and  draught  is  provided  by  one  or  more  fans,  fixed  near 
the  base  of  the  tower,  driven  by  any  convenient  source  of  power,  an 
electric  motor  being  a  favourite  one  in  electricity  generating  works, 
but  a  small  engine,  either  gas,  oil  or  steam,  or  a  strap  from  any  con- 
venient running  shaft  will  also  answer  the  purpose.  The  fan  draught 
tower  is  more  expensive  to  instal,  and  it  is  necessarily  more  expen- 
sive to  work,  because  of  the  power  employed  in  driving  the  fan ;  but 
it  has  the  great  advantage  that  it  is  completely  under  the  control  of 
the  engineer,  within  the  limits  of  the  capacity  of  the  fan,  and  even 
if  a  given  fan  proves  not  to  be  sufficiently  powerful  to  furnish  the 
necessary  draught,  it  is  not  a  great  matter,  in  the  majority  of  cases, 
to  remove  it,  and  fix  a  larger  one.  Fig.  188  shows  a  Balcke  fan- 
cooling  tower. 


376    STEAM   BOILERS,   ENGINES,   AND   TURBINES 


Apparatus  used  in  Cooling  Towers 

The  arrangements  inside  cooling  towers  vary  very  considerably, 
according  to  the   ideas  of  the  different   inventors,   but   as   already 


Vapour 


Vapour  chimney 


Distribution  trough 


FIG.  188.— Balcke  Fan-cooling  Tower. 

explained,  all  of  them  are  intended  to  accomplish  the  same  object — 
the  thorough  breaking  up  of  the  water  to  be  cooled,  into  the  smallest 
possible  particles.  A  favourite  form  consists  of  a  number  of 
V-shaped  channels,  formed  something  like  the  gutters  that  are 
employed  to  carry  off  the  rain  on  the  outside  of  buildings,  the 
gutters  being  placed  one  under  the  other,  and  the  water  being  allowed 
to  fall  gently  into  the  top  gutter,  to  very  gently  overflow  the  edge  of 


CONDENSING  PLANT  377 

the  gutter,  trickling  down  the  outside  of  the  laths  of  which  the 
gutter  is  composed,  from  there  passing  on  to  the  inside  of  the  next 
gutter,  gradually  filling  that,  overflowing  down  the  outer  sides  on  to 
the  next,  and  so  on,  the  idea  being  that  by  overflowing  on  to  the 
outside  of  each  gutter,  and  trickling  down  as  described,  the  water  is 
broken  up  into  fine  drops. 

In  another  form,  a  number  of  wooden  gratings  are  placed  one 
above  the  other,  sometimes  horizontally,  and  sometimes  at  a  slight 
inclination,  the  water  being  sprayed  gently  on  to  the  upper  grating, 
passing  through  the  holes,  and  overflowing  the  sides,  trickling  on 
to  the  undersides  of  the  first  grating,  thence  passing  to  the  second, 
trickling  over  it,  and  so  on  to  the  bottom.  To  be  of  service,  the 
holes  in  the  gratings  in  this  form  of  apparatus  must  be  small,  and 
if  the  water  contains  any  deposit  of  any  kind,  it  tends  to  fill  up  the 
the  holes,  and  to  reduce  the  ability  of  the  gratings  to  break  the  water 
up  into  small  particles. 

Another  form  consists  of  iron  plates,  with  very  small  holes,  the 
water  being  allowed  to  trickle  gently  over  the  plates,  and  through 
the  holes,  the  plates  being  placed  one  above  the  other,  and  a  variation 
of  this  is  a  series  of  wire  gratings  placed  either  horizontally  or  nearly 
horizontally,  the  mesh  of  the  gratings  being  fairly  close,  and  the  water 
trickling  over  and  through  them,  the  bars  of  the  gratings  tending  to 
break  it  up. 

A  further  modification  of  this,  used  in  the  Barnard  cooling  tower, 
consists  of  a  number  of  galvanized  iron  mats,  plaited,  so  as  to  present 
a  large  surface,  with  a  number  of  holes  in  them,  the  mats  being  sus- 
pended vertically  in  the  tower,  in  rows,  the  rows  being  placed  under 
each  other,  as  shown  in  Figs.  186  and  187,  but  with  the  tops  of  the 
second  row  opposite  the  space  between  the  first  row,  successive  rows 
at  right  angles,  and  so  on,  the  water  in  this  case  trickling  over  the 
surfaces  of  the  mats,  and  passing  from  one  mat  to  the  other,  down  to 
the  bottom  of  the  tower. 

Another  arrangement  consists  of  corrugated  or  fluted  iron  plates, 
sometimes  pierced  with  holes,  arranged  as  a  succession  of  inclined 
planes,  leading  from  side  to  side  of  the  tower,  the  upper  plate,  say, 
inclining  from  left  to  right,  the  second  one  from  right  to  left,  and  so 
on.  The  water  is  delivered  gently  to  the  top  of  the  upper  plate, 
over  whose  surface  it  trickles,  part  of  it  passing  through  the  holes, 
and  the  remainder  passing  to  the  bottom  of  the  plate,  and  all  of  it 
passing  on  to  the  second  inclined  plate  over  which  it  trickles,  part 
passing  through  it,  and  so  on. 

Another  method,  employed  by  the  Worthington  Pump  Co.,  con- 
sists of  a  series  of  short  hollow-glazed  earthenware  cylinders,  similar 
to  those  employed  for  drain  pipes,  stacked  in  rows  one  above  the 
other,  and  so  arranged  that  the  edges  of  one  row  are  over  the  middle 


378    STEAM  BOILERS,  ENGINES,  AND   TURBINES 


of  the  next  row,  and  so  on,  the  water  being  delivered  to  the  edges  of 
the  topmost  row,  and  trickling  down  over  the  surfaces  of  the  pipes, 

and  being  broken  up 
as  it  passes,  to  the 
bottom  of  the  tower. 
Eig.  189  shows  a 
Worthington  fan-cool- 
ing tower  made  on 
these  lines. 


A  Convex  Splash 

Bar  Cooling 

Tower 


TOWCf\ 


HOT  WATER, 


Messrs.  Bicbard- 
son,  Westgarth  &  Co. 
have  adopted  a  new 
form  of  apparatus  for 
breaking  up  the  water 
into  very  fine  spray,  in 
the  manner  described 
above,  which  they  have 
called  their  convex 
splash  bar.  From  ex- 
periments which  they 
have  made,  they  state 
that  when  a  drop  of 
water  falls  on  to  an 
inclined  flat  bar,  the 
division  of  the  drop 
into  spray  is  compara- 
tively slight.  They 
say  further,  that  they 
find  that  a  drop  of 
water  falling  on  to  a 
horizontal  flat  bar, 
tends  to  break  up  best, 
but  that  as  the  bar 
FiG.189.—  Worthington  Fan-cooling  Tower,  showing  the  soon  becomes  wet  and 
Earthenware  Pipes  used  for  breaking  up  the  Water  ?  ,,  TT  '  ??a 

to  be  cooled.  holds  a  certain  quantity 

of  th£  water  on  its  sur- 

face, a  bed  or  cushion  is  formed  for  the  later  falling  water,  which 
tends  to  neutralize  any  breaking  up  effect.  To  meet  this  they  have 
designed  a  bar  that  has  a  convex  surface,  and  the  makers  claim  that 


CONDENSING   PLANT  379 

the  drops  of  water  falling  on  the  convex  surface,  are  broken  up  as 
much  as  by  falling  on  a  flat  surface,  on  which  there  is  no  cushion, 
and  that  the  convex  surface  prevents  the  cushion  being  formed. 

The  natural  draught  cooling  towers  made  by  this  firm  are  about 
70  feet  in  height,  the  chimney  portion  being  about  45  feet  high,  the 
water  being  delivered  at  a  height  of  25  feet  to  the  distributing 
troughs. 

Construction  of  Cooling  Towers 

The  early  cooling  towers  were  constructed  of  wood,  mainly,  the 
author  believes,  because  it  was  desired  not  to  spend  more  money  than 
could  be  avoided,  in  what  was  in  those  days  experimental  work. 
Now  that  the  cooling  tower  has  thoroughly  established  itself,  it  is  still 
sometimes  constructed  of  wood,  but  iron,  steel,  and  even  stone  and 
brickwork  are  largely  taking  the  place  of  wood.  Wood,  when 
exposed  to  the  conditions  ruling  in  a  cooling  tower,  wet,  wind, 
weather,  and  sometimes  if  the  tower  is  out  of  use  for  a  time  to 
drying,  does  not  last,  unless  the  wood  itself  is  carefully  chosen,  has 
been  well  seasoned,  and  is  of  a  special  quality  that  will  withstand 
all  these  changes.  Further,  wood,  if  the  tower  is  to  be  made 
sufficiently  strong,  to  continue  in  work  for  the  time  the  works  are 
running,  must  occupy  a  considerable  space.  That  is  to  say,  in  order 
to  provide  the  same  strength  as  with  iron,  steel,  or  even  stone  or 
brick,  the  masses  of  wood  employed  must  be  very  much  larger,  very 
much  more  clumsy,  and  must  occupy  considerably  larger  space.  In 
out-of-the-way  places,  where  appearance  is  not  of  importance,  and 
where  the  works  are  not  likely  to  run  for  a  considerable  time,  as  in 
the  case  of  a  mine  that  may  be  worked  out  at  any  moment,  the  wood 
cooling  tower  is  all  that  can  be  desired,  and  is  probably  the  most 
economical.  But  for  the  cases  of  electricit)*generating  stations  and 
other  works,  where  cooling  of  the  condensing  or  other  water  is  carried 
out  by  the  aid  of  towers,  and  where  appearance  is  of  importance,  and, 
still  more,  where  space  is  of  importance,  stone  or  brick  towers, 
and  still  more  steel  or  iron  towers  are  very  much  more  economical 
and  more  substantial. 

Cooling  towers  are  made  sometimes  rectangular  in  section,  some- 
times circular,  sometimes  of  other  forms.  The  circular  section,  as  in 
every  other  case,  is  probably  the  most  convenient,  and  the  most 
efficient,  though  it  is  very  difficult  to  construct  when  the  tower  is 
of  wood,  hence  the  fancy  for  rectangular  sections  in  wooden  towers. 
When  the  tower  is  of  iron  or  steel,  it  is  built  up  very  much  in  the 
same  manner  as  the  shell  of  a  Lancashire  boiler,  or  an  iron  or  steel 
chimney,  of  rings  made  of  one  or  more  iron  or  steel  plates,  riveted 
together,  the  successive  rings  being  riveted  to  each  other,  the  lowest 


380    STEAM   BOILERS,   ENGINES,   AND   TURBINES 

'  rings  being  arranged  with  a  flange  to  bolt  to  the  foundations,  and  the 
whole  being  fixed  very  much  on  the  lines  of  a  very  large  chimney. 
An  aperture  is  cut  in  one  portion  of  the  side  of  the  tower,  in  which 
the  fan  is  placed. 

When  the  tower  is  constructed  of  stone  or  brick,  it  is  built  very 
much  on  the  lines  of  a  large  low  chimney.  In  some  cases  the  lower 
portion  of  the  tower  is  built  of  stone  or  brick,  and  the  upper  portion 
of  iron  or  steel. 

The  different  portions  of  the  tower  must  be  stayed,  in  the  usual 
way,  and  provision  must  be  made  for  fixing  the  different  cooling 
arrangements  inside,  and  for  the  pipes  for  delivering  the  water,  etc. 

A  somewhat  favourite  form  of  cooling  tower  with  wood,  and 
sometimes  with  iron  structures,  is  of  rectangular  section,  with  a 
vertical  partition  dividing  the  tower  into  two  portions,  and  with  two 
separate  fans  or  other  provisions  for  furnishing  the  necessary  draught. 
This  arrangement  allows  for  heavy  loads,  or  for  a  lowered  efficiency 
of  the  tower  under  the  atmospheric  conditions  that  have  been  named. 
Thus  one  half  of  the  tower  can  be  employed  under  ordinary  working 
conditions,  and  both  halves  under  special  conditions,  the  two  halves 
being  used  alternately  to  keep  them  in  working  order.  It  will  be 
noticed  that  in  all  arrangements  of  cooling  towers  where  vertical 
draught  rules,  the  air  current  and  the  water  current  are  in  opposite 
directions.  This,  as  already  explained,  is  the  rule  in  all  cases  where 
it  is  possible,  where  heat  is  to  be  abstracted  from  any  moving  body. 
The  coldest  air  entering  the  tower  at  the  bottom  meets  the  coldest 
water  that  has  been  subjected  to  the  cooling  effect  of  the  evapo- 
ration that  has  been  taking  place  during  its  descent  through  the 
tower,  while  the  hottest  water  meets  the  warmest  air  as  it  enters  the 
tower.  It  will  be  understood  that,  as  with  the  cooling  ponds,  a 
certain  quantity  of  water  is  lost  by  evaporation,  and  is  carried  off  by 
the  draught  and  delivered  to  the  outside  atmosphere.  It  has  been 
estimated  that  with  properly  proportioned  cooling  towers,  the  loss  of 
water  varies  from  1/2  to  2*5  gallons  per  indicated  H.P.  per  hour, 
according  to  the  force  of  draught  employed.  It  will  be  understood 
again  that  the  quantity  of  water  evaporated,  and  therefore  the  cool- 
ing effect  produced,  varies  directly  with  the  velocity  of  the  air 
current  passing  through  the  tower,  that  is  to  say,  directly  as  the 
draught.  Each  cubic  foot  of  air  properly  applied  absorbs  a  certain 
quantity  of  watery  vapour,  and  therefore  the  higher  the  velocity  of 
the  air,  the  greater  is  the  absorption  of  vapour.  This,  however,  only 
applies  up  to  a  certain  point,  though  the  actual  limit  has  not  yet  been 
determined. 


INDEX 


Absolute  pressure,  definition  of,  22 
Absolute    temperature    on     Centigrade 

scale,  5 
Absolute    temperature    on    Fahrenheit 

scale,  5 

Absolute  unit  of  heat,  14 
Absorber  flange  seam  boiler  flues,  Adam- 
son,  63 

Absorption  of  heat,  10 
Absorption  of  water  vapour  by  air,  25 
Action  of  steam  in  pressure  turbine,  292 
Action  of  steam  on  water  in  pockets,  278 
Action  steam  turbine,  289 
Actinic  rays,  3 
Adamson   absorber   flange    seam    boiler 

flues,  63 

Adamson  joint,  boiler  flues,  63 
Adamson,  Daniel,  triple-expansion  mill 

engine,  240 
Adaptability    of    turbines    for    exhaust 

steam,  323 

Adibiatic  expansion  of  steam,  290 
Adjustable  nozzle  for  steam  jet  draught, 

148 

Admission  of  steam  to  intermediate  sec- 
tions of  turbine,  295 
Advantages  claimed  for  corrugated  boiler 

furnaces,  65 

Advantages   claimed    for   Fraser's    con- 
denser, 336 

Advantages  claimed  for  steam  jets,  147 
Advantages  of  circular  chimneys,  137 
Advantages  of  ejector  condenser,  344 
Advantages  of  induced  draught,  143 
Advantages  Lanes,  boiler  over  water-tube, 

78 

Advantages  of  mechanical  stokers,  115 
Advantages  of  multitubular  boilers,  71 
Advantages  of  parallel  slide  stop  valve,  257 
Advantages  of  superheated  steam  in  tur- 
bines, 328 
Advantage   of    water-tube    boilers   with 

high  pressures,  79 
Advantages  of  vacuum  augmenter,  347 


A.E.G.  turbine,  construction  of,  316 

A.E.G.  turbine,  course  of  steam  in,  316 

Air,  composition  of,  25 

Air  and  absorption  of  water  vapour,  25 

Air  and  the  economizer  chamber,  163 

Air  and  heat  conduction,  10 

Air  and  heat  absorption,  11 

Air  at  various  temperatures,  volume  and 

weight  of,  26 

Air  cells  in  thermal  insulators,  13 
Air  cylinder  in  Willans  engine,  233 
Air,  effect  of,  in  surface  condenser,  332 
Air,  expansion  and  contraction  with  tem- 
perature, 25 
Air  for  the  furnace,  methods  of  providing, 

127 

Air  heating  with  forced  draught,  139 
Air  heating  and  induced  draught,  143 
Air  leakage  and  boiler  brickwork,  69 
Air  leakage  in  boiler  flues,  143 
Air  leakage  and  induced  draught,  143 
Air^power  required  to  move,  147 
AirT^roperties  of,  25 
Air  pumps,  bucket,  366 
Air  pump  capacity  for  condenser,  Kichard 

Allen,  356 
Air  pump  capacity  for  condenser,  Prof. 

Weighton,  361 

Air  pumps,  dry,  two  stage,  365 
Air  pumps  for  condenser,  365 
Air  pump,  Edwards,  operation  of,  366 
Air  pump  with  Fraser's  condenser,  336 
Air  pump  for  jet  condenser,  340 
Air  pump  for  surface  condenser,  331 
Air  required  for  combustion  of  fuel,  130 
Air  required  with  forced  draught,  141 
Air,  saturation  by  water  vapour,  27 
Air,  specific  heat  of,  29 
Air  supply  with  Fraser's  condenser,  336 
Air,  temperature   outside   and  chimney 

draught,  134 
Air    and    water    heating    economisers, 

arrangement  of,  162 
Air,  weight  of,  18 
Allen's  high-speed  engines,  construction 

of,  229 


381 


382 


INDEX 


Allen,  Richard,  condenser  experiments, 

352 

Alphonse  Custodis  chimneys,  138 
Alternating  current   generators,   use    of 

stop  valve  in  driving,  243 
Analysis,  flue  gas  apparatus,  Orsat,  212 
Analysis  of  water  and  water  softening, 

182 
Anderson  steam  trap,   construction   of, 

286 

Angle  of  incidence,  4 
Angle  of  refraction,  4 
Angle  stop  valves,  255 
Anthracite  coals,  properties  of,  42 
Apparatus  for  burning  coal  dust,  110 
Apparatus   for   burning  liquid   fuel,  49, 

111 

Apparatus,  Davis-Perrett,  sizes  of,  199 
Apparatus,  Orsat,  for  flue  gas  testing,  212 
Apparatus    for    removing    oil,     Harris- 
Anderson,  198 

Apparatus,  special,  for  removing  oil,  197 
Apparatus  used  in  cooling  towers,  376 
Apparatus,  water  safety,  155 
Approximate  analysis  of  fuel,  43 
Archbutt-Deely   apparatus,    carbonating 

water  in,  184 

Archbutt-Deely  apparatus,  mud  precipi- 
tate, 184 
Archbutt-Deely  apparatus,  operation  of, 

184 
Archbutt-Deely  apparatus,  special  feature 

of,  183 

Archbutt-Deely  water  softener,  183 
Area  grate  of  furnace  required,  132 
Arrangement  of  air  and  water  heating 

economizers,  167 
Arrangement     of     central     condensing 

stations,  348 
Arrangement  of  cranks  with  ram  pumps, 

170 
Arrangement  of  cranks,  Willans  engine, 

233 

Arrangement  of  Curtis  turbine,  311 
Arrangement  of  cylinders,  quadruple - 

expansion  engines,  227 
Arrangement  of  cylinders   in  triple-ex- 
pansion engines,  "226 
Arrangement    of    cylinders    in    Willans 

engine,  232 
Arrangement  of  fan  with  induced  draught, 

141 

Arrangement  of  Holden  liquid  fuel  ap- 
paratus, 112 

Arrangement  of  rings  of  boiler  shells,  62 
Arrangement  of  steam  pipes,  278 
Arrangement  of  steam  and  water  pipes 

in  ejector  condenser,  344 
Arrangement  of  triple-expansion  engines, 
226 


Arrangement     of     tubes,     Thornycroft- 

Schultz  boiler,  101 
Arrangement  of  worm  gearing,  265 
Ash,  effect  of,  on  calorific  value,  41 
Ashpit  in  Lanes,  boilers,  59 
Ashpits  in  water-tube  boilers,  82,  107 
Asphalt,  47 

Atlas  boiler,  course  of  hot  gases,  94 
Atlas  boiler,  drums  in,  93 
Atlas  boiler,  feed  water,  93 
Atlas  boiler,  headers  in,  93 
Atlas  boiler,  superheating,  94 
Atlas  boiler,  water  purifying  apparatus, 

95 

Atlas  water-tube  boiler,  93 
Atmosphere,  composition  of,  18 
Atmosphere,  gases  in,  18 
Atmosphere,  variation  in  pressure  of,  19 
Atmosphere  and  water  vapour,  18 
Atmospheric  line  on  indicator  cards,  272 
Atmospheric    pressure    and     mercurial 

barometer,  18 
Atmospheric  pressure,  specified  heat  of 

superheated  steam  at,  36 
Atmospheric  pressure,  standard,  18 
Atmospheric  relief  valve,  155 
Augmenter,  Parsons,  vacum,  347 
Automatic  CO*  recorder,  Sarco,  208 
Automatic  damper  regulators,  149 
Auto  stoker,  construction  of,  122 
Auto  stoker,  fire  bars  in,  123 
Axle  of  Brush-Parsons  turbine,  301 


Babcock  boiler,  construction  of,  82 
Babcock  boiler,  course  of  hot  gases  in,  83 
Babcock  boiler,  headers  in,  83 
Babcock  boiler,  steam  drums  in,  83 
Babcock  boiler,  superheater,  83 
Babcock  chain-grate  stoker,  construction 

of,  125 

Babcock  marine  boiler,  83 
Babcock  superheater,  200 
Babcock  water-tube  boiler,  82 
Back  pressure,  mean  in  cylinder,  218 
Bagasse,  calorific  value  of,  45 
Bailey's  reducing  valve,  259 
Balanced  slide  valves,  248 
Balancing  discs  in  steam  turbine,  295 
Balcke's  chimney  cooling  tower,  373 
Balcke's  fan  cooling  tower,  376 
Balcke's  jet  condenser.  340 
Barnard  chimney  cooling  tower,  373 
Barometer  indications  and  water  vapour 

in  atmosphere,  19 
Barometer,  mercurial,  18 
Barometric  condenser,  344 
Barometric  condenser,  Bulkley,  345 


INDEX 


383 


Barometer  condenser,  cooling  water  for, 

346 
Barometric  condenser,  course  of  steam 

in,  345 

Barometric  condenser,  operation  of,  344 
Barometric  condenser,  pump  for,  346 
Bars,  furnace,  special  forms  of,  108 
Bearings  of  Brush-Parsons  turbine,  301 

Bearings  of  Curtis  turbine,  311 

Bearings  of  Hamilton  Holzwarth  turbine, 
321 

Bearings  of  Parsons  turbine,  construc- 
tion of,  295 

Bearings  of  Zoelly  turbine,  319 

Beds  of  streams,  surface  condensers  for, 
336 

Belliss  engines,  construction  of,  229 

Belt,  double,  formula  for,  264 

Belt  drive,  efficiency  of,  265 

Belt  driving  and  crank  shaft,  262 

Belt  driving,  pulleys  for,  262 

Belt,  driving  side  of,  263 

Belt,  how  power  is  transmitted  by,  262 

Belt  pulleys,  heating  of,  263 

Belt,  size  of,  formula  for,  263 

Belt,  slipping  of,  263 

Belt,  tight  side  and  loose  side,  263 

Bennis  mechanical  stoker,  122 

Bi-carbonates,     temperature    at,     when 
splitting  up,  33 

Bituminous  coals,  composition  of,  42 

Bituminous  coals,  properties  of,  41 

Blades  of  Willans  turbine,  construction 
of,  293 

Blast  furnace  gas,  calorific  value  of,  51 

Blast  furnace  gas,  composition  of,  51 

Blast  furnace  gas,  production  of,  50 

Blast  furnace  gas,  use  of,  50 

Board  of  Trade  formula  for  boiler  fur- 
naces, 65 

Board  of  Trade,  powers  of,  68 

Bodies  in  mechanical  suspension  in  water 
and  boiling  point,  21 

Boiler,  Babcock,  course  of  hot  gases,  83 

Boiler,  Babcock,  superheater,  83 

Boilers  and  brickwork,  68 

Boiler  brickwork  and  air  leakage,  69 

Boiler  brickwork,  McLeod  and  Henry,  69 

Boiler  for  burning  refuse,  Galloway,  70 

Boiler  chimneys,  construction  of,  137 

Boiler  chimneys,  forms  of,  137 

Boiler  cleaners,  construction  of,  150 

Boiler  cleaners,  reason  for,  150 

Boilers,  Cornish,  setting,  68 

Boiler,  dry  back,  72 

Boilers,  electrolytic  action,  181 

Boiler  feed  and  exhaust  from  turbines, 
329 

Boiler  feed  pumps,   electrically  driven, 
172 


Boiler  feed  and  scale  forming  substances ' 

181 

Boiler  feed,  use  of  cooling  water  for,  333 
Boiler  fittings,  enumeration  of,  151 
Boiler  flues,  absorber  flange  seam,  Adam- 
son,  63 

Boiler  flues,  Adamson  joint,  63 
Boiler  flues,  air  leakage  with,  143 
Boiler  flues,  construction  of,  63 
Boiler  flues,  Cornish,  63 
Boiler  flues,  corrugated,  64 
Boiler  flue  dampers,  148 
Boiler  flues,  joints  of,  63 
Boiler  flue  joint,  Davey-Paxman,  64 
Boiler  flues,  Lanes.,  63 
Boiler  furnace  cambered,  John  Brown,  65 
Boiler  furnace,  colliery  refuse,  Meldrum, 

70 

Boiler  furnaces  corrugated,  64 
Boiler  furnaces  corrugated,   advantages 

claimed  for,  65 
Boiler  furnaces,  doors  of,  108 
Boiler  furnaces,  effect  of  water  vapour  in 

air,  27 
Boiler  furnaces,  formula,  Board  of  Trade, 

65 

Boiler  furnace  formula,  British  Corpora- 
tion, 65 
Boiler  furnace,  formula,  Bureau  Veritas, 

65 

Boiler  furnaces  formula,  Lloyd's,  65 
Boiler  furnace  improved,  John  Brown,  65 
Boiler  furnace,  methods  of  providing  air 

for,  127 

Boiler  furnace,  Morrison  suspension,  65 
Boiler  furnace,  pressure  of  air  creating 

draught,  28 
Boiler  furnaces,  sizes   of,  with  working 

pressures,  67 
Boiler  furnace,  steam  jets,  arrangement 

of,  147 

Boiler  furnaces,  tests  of,  65 
Boilers,  heating  feed  water  for,  156 
Boilers,  horse  power  of,  discussed,  132 
Boilers,  Lanes.,  setting,  68 
Boiler,  locomotive,  72 
Boiler,  locomotive,  construction  of,  73 
Boiler,  marine,  72 
Boiler,  marine,  Babcock,  83 
Boiler,  motor-wagon,  White,  106 
Boiler  plate  punching,  61 
Boiler,  Robb-Mumford,  construction  of, 

76 

Boiler  shells,  building  up,  61 
Boiler  shells,  butt  joints,  61 
Boiler  shells,  drilling,  61 
Boiler  shells,  joints  in,  61 
Boiler  shells,  lap  joints,  61 
Boiler  shells,  riveting,  62 
Boiler,  Stirling  drums  of ,  86 


INDEX 


Boiler,  Stirling,  superheater,  86 
Boiler,  Thornycroft-Marshall,  100 
Boiler,  Thornycroft-Schultz,  100 
Boiler-tube  cleaners,  turbine,  151 
Boiler-tube  cleaner,  Wynland,  150 
Boiler-tube  cleaning  by  steam  jet,  151 
Boilers,  vertical,  small,  104 
Boiler  water  gauge,  construction  of,  151 
Boiler,  water-tube,  Atlas,  |93] 
Boiler,  water-tube,  Babcock,  82 
Boiler,  water-tube,  brickwork,  78 
Boilers,  water-tube,  circulation,  81 
Boiler,  water-tube,  Climax,  98 
Boilers,    water-tube,     convenience     for 

transporting,  81 

Boiler,  water-tube,  Davey-Paxman,  91 
Boilers,  water-tube,  furnace  of,  82 
Boiler,  water-tube,  Galloway,  93 
Boilers,     water-tube,     with     horizontal 

tubes,  90 

Boiler,  water-tube,  Marshall,  91 
Boiler,  water-tube,  Nesdrum,  87 
Boiler,  water-tube,  Stirling,  84) 
Boiler,  water-tube,  Taylor,  104 
Boiler,  water-tube,  Thornycroft,  99 
Boiler,  water-tube,  Wood,  92 
Boiler,  water-tube,  Woodeson,  88 
Boiler,  wet  back,  74 
Boiler,   working,  effect    of    scale   upon, 

181 

Boiler  work,  pressure  required  for,  130 
Boiling,  operation  of,  19 
Boiling-point  on  Centigrade  scale,  4 
Boiling-point    and  effect  of  pressure  on 

surface  of  liquid,  19 

Boiling-point  on  Fahrenheit  pressure,  4 
Boiling-point  on  Reaumur  pressure,  4 
Boiling-point,  standard  level  for,  18 
Boiling-point,  standard  pressure  for,  18 
Boiling-point,  variation  of,  18 
Boiling-point    of    water    and   bodies    in 

mechanical  suspension,  21 
Boiling-point  of  water  and  dissolved  sub- 
stances, 21 

Boiling-point  of  water  at   various   alti- 
tudes, 20 
Boiling  temperature,   increase   of,  with 

pressure,  21 
Brake  horse-power,  219 
Brake  horse-power,  measurement  of,  220 
Brass  and  iron,  expansion  of,  6 
Brasses  in  compression,  Willans  engine 

233 

Brickwork  with  water-tube  boilers,  78 
Bridge  in  furnace  grates,  107 
Bristol's  thermo-electric  pyrometer,  9 
British  Corporation,  explanation  of,  68 
British  Corporation  formula  boiler  fur- 
nace, 65 
British  thermal  unit,  definition  of,  13 


British    thermal    unit   and    the    horse- 
power, 15 

Brooke's  steam  trap,  construction  of,  281 
Brooke's  steam  trap,  operation  of,  281 
Brotherhood  engines,  construction  of,  229 
Browett  engines,  construction  of,  229 
Brown  coals,  composition  of,  41 
Brown,  John,  cambered  boiler  furnace, 

65 

Brown,  John,  improved  boiler  furnace,  65 
Brunn-Lowener  water  softener,  construc- 
tion of,  187 

Brush-Parsons  turbine,  300 
Brush-Parsons  turbine  bearings,  301 
Brush-Parsons  turbine,  control  of  steam 

to,  301 

Bucket  air  pumps,  366 
Bucket  in  Edwards  air  pump,  366 
Buckets  of  steam  turbines,  forms  of,  322 
Building  up  boiler  shells,  61 
Bulkley  barometric  condenser,  345 
Bumsted  engine,  double  acting,  237 
Bumsted  engine,  forms  of,  236 
Bumsted  engine,  lubrication  of,  236 
Bumsted  engine,  single  acting,  236 
Bumsted  high  speed  engine,  236 
Bureau  Veritas  formula,  boiler  furnace, 

65 

Bureau  Veritas,  powers  of,  68 
Burning  liquid  fuel,  apparatus,  49,  111 
Burning  refuse,  boiler,  Galloway,  70 
Burning  town's  refuse,  113 
Burning  town's  refuse,  draught  with,  114 
Butt  joints  boiler  shells,  61 


Calorie,  14 

Calorific  power,  explanation  of,  38 
Colorific  value  of  bagasse,  45 
Calorific  value  of  blast  furnace  gas,  51 
Calorific  value  of  coke-oven  gas,  51 
Calorific  value  of  corn,  46 
Calorific  value  of  cotton,  46 
Calorific  value,  effect  of  nitrogen  on,  41 
Calorific  value,  explanation  of,  38 
Calorific  value  formula,  Dulong,  39 
Calorific  value  of  gas  tar,  48 
Calorific  value  of  natural  gas,  52 
Calorific  value  of  producer  gas,  50 
Calorific  value  of  spent  tan,  45 
Calorific  value  of  straw,  45 
Calorific  value  of  town's  refuse,  113 
Calorific  value  of  wood,  45 
Calorimeter,  Thomson's,  44 
Calorimeters,  description  of,  44 
Calorimetry,  explanation  of,  44 
Cannel  coal,  composition  of,  41 
Capacity  of  air  for  water  vapour,  law  of, 
25 


INDEX 


385 


Carbon  and  oxygen,  combustion,  37 
Carbonates  and  bi-carbonates  in  water,  33 
Carbonate  of  calcium  in  water,  33 
Carbonate  of  magnesium  in  water,  33 
Carbonating    water    in    Archbutt-Deely 

apparatus,  184 

Carbonic  acid  and  heat  absorption,  11 
Carbonic  acid,  heat  liberated  in  forming, 

38 

Carbonic  acid  and  water,  33 
Carbonic  oxide  and  heat  absorption,  11 
Carbonic  oxide,  heat  liberated  in  forma- 
tion of,  38 

Care  of  economizers  in  frosty  weather,  162 
Carnot's  law  of  heat  engines,  36 
Carter's  economizer,  construction  of,  160 
Cause  of  waste  in  domestic  fire  grate,  54 
Celsius  scale,  4 

Centigrade  scale,  divisions  of,  4 
Centigrade  scale,  limits  of,  4 
Central  condensing  plant  with  cooling 

tower,  350 

Central  condensing  stations,  348 
Central  condensing   stations,   operation 

of,  349 

Central  Engineering  Co.'s  evaporator,  205 
Central  pressure  stop  valve,  Hopkinson, 

257 
Central  pressure  stop  valve,  operation  of, 

257 

Central  valve  engine,  Willans,  232 
Centrifugal  fan,  construction  of,  146 
Centifrugali  fan,   pressure  in,   how  pro- 
duced, 146 

Centrifugal  pump  for  condenser,  363 
Chain-grate  mechanical  stokers,  124 
Chart  of  Simmance  recorder,  211 
Chemical  action  in  combustion,  37 
Chemical  rays,  3 

Chimney  cooling  tower,  Balcke,  373 
Chimney  cooling  tower,  Barnard,  373 
Chimney  cooling  towers,  forms  of,  374 
Chimney  cooling  towers,  height  of,  375 
Chimney  cooling  towers,  operation  of,  372 
Chimney  cooling  tower,  pressure  in,  373 
Chimney  cooling  towers,  sizes  of,  375 
Chimney  draught,  explanation  of,  127 
Chimney  draught  and  motive  column,  128 
Chimney  draught,  seasons,  effect  of,  135 
Chimney  draught   and    temperature    of 

outside  air,  134 
Chimney    gases,    temperature    of,   with 

forced  draught,  140 
Chimney,   height   of,    and   intensity   of 

draught,  137 

Chimney  pressure,   with   different  tem- 
peratures outside,  134 
Chimney,  temperature  of  hot  gases  in, 

129 
Chimney,  testing  flue  gases  in,  205 


Chimneys,  Alphonse  Custodis,  138 
Chimneys,  boiler,  construction  of,  137 
Chimneys,  boiler,  forms  of,  137 
Chimneys,  circular,  advantages  of,  137 
Chimneys,  circular  and  other  forms,  137 
Chimneys,  effective  area  of,  135 
Chimneys,  foundations  of,  138 
Chimneys,  height  of,  132 
Chimneys,  height  of,  Kent's  table  for,  135 
Chimneys,  loss  of  energy  in,  131 
Chimneys  and  radial  bricks,  138 
Chimneys,  requirements  of,  131 
Chimneys,  sectional  area  of,  132 
Chimneys,  standard  for,  Prof.  Thurston, 

132     ' 

Chimneys,  steel,  construction  of,  138 
Chimneys  and  water  tanks,  138 
Chlorides  and  water,  33 
Circular  chimneys,  advantages  of,  137 
Circular  and  other  forms  of  chimney, 

proportion  between,  137 
Circulating  pump  for  surface  condenser, 

331 
Circulating  pump,  variation  of  speed  for 

condenser,  363 
Circulating  water  for  condensers,  cooling, 

367 
Circulating    water,    velocity    of,     Prof. 

Weighton,  362 
Circulation    in    boilers    by    convection 

currents,  54 

Circulation  in  boilers,  explanation  of,  54 
Circulation  in  boilers,  importance  of,  54 
Circulation  of  water,  Climax  boiler,  99 
Circulation  in  water-tube  boilers,  81 
!  Classes  of  steam  turbine,  288 
Cleaning  deposit  from  economizer  tubes, 

159 

Cleaning  of  filter  in  Reisert  water  soft- 
ener, 186 

Clearance  in  Bateau  turbine,  316 
Clearance  in  Zoelly  turbine,  319 
Climax  boiler,  construction  of,  98 
Climax  boiler,  course  of  hot  gases,  99 
Climax  boiler,  feed  water  heater,  99 
Climax  boiler,  steam  drum,  99 
Climax  boiler,  water  circulation,  99 
Climax  boiler,  water  tubes  of,  98 
Climax  water-tube  boiler,  79,  98 
Closed  ashpit  system  of  forced  draught, 

139 

Closed  ashpit  system,  objections  to,  139 
Closed  fire  room  system  of  forced  draught 

139 
Closed    stoke-hole     system     of     forced 

draught  139 
Clouds,  formation  of,  32 
Coal,  description  of,  39 
Coals,  differences  between,  42 
Coal  dust  burning  apparatus,  110 
2   C 


386 


INDEX 


Coal  dust  burning  apparatus,  Cyclone,  111 
Coal  dust  burning  apparatus,  Schwartz- 

kopff,  111 

Coal  dust  furnace,  Meldrum,  110 
Coal,  forms  of,  40 
Coals,  gradation  of,  41 
Coal  saved  by  condensing,  Richard  Allen, 

355 

Coals,  volatile  matter,  42 
Cochrane  vacuum,  oil  separator,  195 
Coke  oven  gas,  calorific  value  of,  51 
Coke  oven  gas,  production  of,  51 
Coker  mechanical  stokers,  rams  of,  119 
Coker  mechanical  stokers,  shovels  of,  119 
Coker  stoker,  Meldrum,  119 
Coking  mechanical  stokers,  117 
Colliery  refuse  destructor,  Meldrum,  114 
Colliery  refuse,  furnace,  Meldrum's,  70 
Column  of  air  above  the  earth,  weight  of, 

18 
Combination  of  exhaust  and  live  steam, 

325 

Combined  boiler,  construction  of,  76 
Combined  condenser  and  pump  plant, 

Wheeler,  337 
Combined    Cornish    and    multitubular 

boiler,  76 

Combined  stop  and  safety  valve,  156 
Combustion,  chemical  action,  37 
Combustion,  combination  of  carbon  and 

oxygen,  37 

Combustion  in  domestic  fire  grate,  53 
Combustion  fuel  in  furnace,  37 
Combustion,  volume  of  gases  produced 

by,  130 

Comparison  of  mean  pressures  with  vary- 
ing cut-offs,  215 

Composition  of  bituminous  coals,  41 
Composition  of  blast  furnace  gas,  51 
Composition  of  brown  coals,  41 
Composition  of  cannel  coal,  41 
Composition  of  gas  tar,  48 
Composition  of  natural  gas,  52 
Composition  of  peat,  40 
Composition  of  petroleum,  46 
Composition  of  producer  gas,  50 
Composition  of  semi-bituminous   coals, 

41 

Composition  of  wood,  44 
Compound  condensing   engine,   tandem 

horizontal,  224 
Compound   Cornish  boiler,   Fraser   and 

Chalmers,  76 
Compound     engines,    arrangement    of, 

Willans  engine,  234 
Compound  engine,  course  of  steam  with, 

221 

Compound  engines  described,  221 
Compound  engines,  horizontal,  arrange- 
ment of,  239 


Compound  engine,  proportion  of  cylin- 
ders in,  221 
Compound  engine,  tandem,   horizontal, 

223 

Compound  pressure  turbines,   construc- 
tion of,  292 
Compound  vertical  engines,  arrangement 

of,  239 
Compound  vertical  engine,  unenclosed, 

225 

Compounding  in  pressure  turbines,  292 
Compressed  air,   and    heat   in    Willans 

engine,  234 
Compressed  air  machinery,  engines  for 

driving,  239 
Compressing  air,  work  in  Willans  engine, 

234 
Condensation  in  cylinder,  with  expansive 

working,  215 

Condensation  of  water  vapour,  34 
Condensed  water  for  feed,  objection  to, 

169 
Condenser,  air  pump  capacity,  Richard 

Allen,  356 
Condenser,  barometric,  cooling  water  for, 

346 
Condenser,  barometric,  course  of  steam 

in,  345 
Condenser,  barometric,  course  of  water 

in,  345 

Condenser,  barometric,  operation  of,  344 
Condenser,  centrifugal  pump  for,  363 
Condensers,  circulating  water  for,  cool- 
ing, 367 

Condenser,  Contraflo,  338 
Condenser,  cooling  surface,  and  I.H.P., 

352 
Condenser,     cooling     surface,     Richard 

Allen,  356 

Condenser,  counter-current,  jet,  340 
Condenser,  dry  air  pump  for,  365 
Condenser    efficiency,    Prof.   Weighton, 

361 

Condenser,  ejector,  operation  of,  343 
Condenser  employed  by  Prof.  Weighton, 

360 
Condenser  experiments,  Richard  Allen, 

352 
Condensers,      experiments      on,      Prof. 

Weighton,  360 

Condenser,  evaporative,  Fraser,  335 
Condensers  fixed  in  Lanes,  mill  engines, 

241 

Condenser,  jet,  air  pump  for,  340 
Condenser,  jet,  Balcke,  340 
Condenser,  jet,  counter  current,  340 
Condenser,  jet,  Mirrlees- Watson,  341 
Condenser,  jet,  parallel  current  340 
Condenser,  jet,  pumps  for,  340 
Condenser,  jet,  versus  surface,  341 


INDEX 


387 


Condenser,  jet,  Worthington,  velocity  of 

steam  in,  343 

Condenser,  operation  of,  330 
Condenser,  plunger  pumps  for,  363 
Condensers,  pumps  for,  363 
Condenser,  pump  and  electric  motor,  363 
Condenser  and   pump   plant   combined, 

Wheeler,  337 

Condenser  with  solid  wooden  cores,  360 
Condensers,    surface,    for    the    beds    of 

streams,  338 

Condenser,  surface,  construction  of,  331 
Condenser,    surface,     evaporative,    con- 
struction of,  334 

Condensers,  surface,  open  tank,  338 
Condenser,  surface,  Wheeler,  336 
Condenser,  use  of,  330 
Condenser  for  use  with  De  Laval  turbine, 

309 
Condenser,  velocity  of  circulating  water 

in,  Prof.  Weighton,  362 
Condenser,  velocity  of  cooling  water  in, 

352 
Condensing,  coal  saved  by,  Richard  Allen, 

355 
Condensing  cooling  water,  quantity  of, 

349 
Condensing,  cooling  water  required  for, 

Prof.  Weighton,  361 
Condensing,  economy  of  with  different 

steam  pressures,  367 
Condensing     engine,      cross-compound, 

horizontal,  224 
Condensing  plant,  central,  with  cooling 

tower,  350 
Condensing   plant,   power  absorbed  by, 

367 
Condensing  plant,  steam  consumption, 

Richard  Allen,  355 

Condensing    stations,    central,   arrange- 
ment of,  348 
Condensing  stations,  central,  operation 

of,  349 
Condensing,  triple-expansion  mill  engine 

horizontal,  240 
Condensing  and  turbines,  327 
Conditions  of  matter  explained,  17 
Conduction  of  heat,  9 
Conductive  powers  of  metal,  11 
Conductivity,  thermal,  definition  of,  11 
Conductivity  thermal,  of  finely  divided 

substances,  12 

Connection  of  trap  to  steam  service,  280 
Constant  ratio  of  refraction,  3 
Consumption  of  steam,De  Laval  turbine, 

302 
Consumption,     steam,    with     different 

vacua,  Richard  Allen,  353,  354 
Consumption  of  steam  in  vacuum  aug- 

menter,  348 


Contraction    and    expansion    of    steam 

pipes,  279 
Contraflo  condenser,   course  of  cooling 

water  in,  339 
Contraflo  condenser,  course  of  steam  in, 

339 

Contraflo  condenser,  operation  of,  339 
Contraflo  condenser,  vapour  distribution 

chambers  in,  339 

Control  of  air  by  flue  dampers,  148 
Control  of  steam  for  Brush-Parsons  tur- 
bine, 308 

Control  of  steam  supply  by  governor,  243 
Control  of  steam  supply  by  stop  valve,  243 
Convection  currents,  9 
Convection  currents  in  boilers,  54 
Convenience  water-tube  boilers  for  trans- 
porting, 81 
Conversion    of     potential    into    kinetic 

energy,  289 
Convex  splash  bars  for   cooling  towers, 

378 
Cooling  circulating  water  for  condensers, 

367 

Cooling  the  cooling  water,  333 
Cooling  effect  of  evaporation  of  water, 

335 

Cooling  of  furnace  bars  by  steam  jets,  147 
Cooling  ponds,  evaporation  from,  369 
Cooling  ponds  and  Lanes,  cotton  mills, 

368 

Cooling  ponds,  louvre  boards  for,  370 
Cooling  ponds  with  nozzles,  369 
Cooling  surface  in  condenser  per  I.H.P., 

352 
Cooling  surface  in  condenser,  Richard 

Allen,  356 
Cooling  towers,  370 
Cooling  towers,  apparatus  used  in,  376 
Cooling  tower  and   central    condensing 

plant,  350 

Cooling  tower,  chimney,  Balcke,  373 
Cooling  tower,  chimney,  Barnard,  373 
Cooling  tower,  chimney,  height  of,  375 
Cooling  tower,  chimney,  size  of,  375 
Cooling  towers,  construction  of,  379 
Cooling  .towers,  convex  splash  bars  for, 

378 
Cooling  towers,   corrugated  iron  plates 

in,  377 

Cooling  towers,  course  of  air  in,  380 
Cooling  towers,  course  of  water  in,  380 
Cooling  towers,  duplicate,  380 
Cooling  tower  with  fan  draught,  375 
Cooling  towers,  forms  of,  379 
Cooling  towers,  galvanized  iron  mats  in, 

377 

Cooling  towers,  iron  for,  379 
Cooling  towers,  iron  plates  in,  377 
Cooling  tower  and  jet  condenser,  340 


INDEX 


Cooling  towers,  loss  of  water  in,  380 
Cooling  towers,  operation  of,  371 
Cooling  towers  without  vertical  draught, 

protection  of,  371 
Cooling  towers,  wood  for,  379 
Cooling  towers,  wooden  gratings  in,  377 
Cooling  tower,  Worthington  Co.,  377 
Cooling  water  for  barometric  condenser, 

346 
Cooling  water  for  condensing,  quantity 

of,  349 

Cooling  water,  heat  absorbed  by,  333 
Cooling  water  with  high  vacua,  351 
Cooling  water,  limiting  temperature  of, 

332 
Cooling  water  required  with  condensers, 

formula  for,  351 
Cooling  water  required  for  condensing, 

Prof.  Weighton,  361 
Cooling  water  required    with    different 

vacua,  Richard  Allen,  356 
Cooling  water  required  and  initial  tem- 
perature, 351 

Cooling  water  velocity  in  condenser,  352 
C02  recorder,  Sarco,  208 
C02  recorder,  Simmance,  210 
Cork,  properties  of,  13 
Corliss  valve,  242 
Corliss  valve,  description  of,  251 
Corliss  valve  and  eccentric  rod,  252 
Corliss  valve,  operation  of,  251 
Corliss  valve,  wrist  plate  of,  252 
Corn,  calorific  value  of,  46 
Cornish  boilers,  construction  of,  60 
Cornish  boilers,  description  of,  55 
Cornish  boilers,  ends  of,  62 
Cornish  boilers,  external  furnaces,  69 
Cornish  boilers,  firing,  69 
Cornish  boiler  flues,  56,  63 
Cornish  boilers,  furnace  grates,  107 
Cornish  boilers,  hot  gases,   passage   of, 

56 

Cornish  boilers,  setting,  68 
Cornish  boilers,  sizes  of,  62 
Cornish  boilers,  steam  space,  58 
Cornish  boilers,  water  in,  58 
Cornish  and  multitubular  boiler,  76 
Cornish  pumps,  driving,  260 
Cornish  pumping  engines,  213 
Cornish  valve,  242 
Cornish  valves,  description  of,  250 
Cornish  valve,  operation  of,  251 
Cornish  versus  Lanes,  boiler,  60 
Corrugated  boiler  flues,  64 
Corrugated  boiler  furnaces,  64 
Corrugated  boiler  furnaces,   advantages 

claimed  for,  65 
Corrugated  iron  plates  in  cooling  towers, 

377 
Corrugated  tube,  Wainwright,  166 


Cost  of  circulating  water,  Prof.  Weighton, 

363 

Cost  of  producing  forced  draught,  141 
Cost  of  water  for  condensing,  368 
Cotton,  calorific  value  of,  46 
Counter-current  jet  condensers,  340 
Cranks,  arrangement  of,  Willans  engine, 

233 

Crank,  construction  of,  260 
Crank,  dead  points  of,  261 
Cranks  and  double-cylinder  engines,  261 
Crank,  length  of  radius  of,  261 
Crank,  operation  of,  261 
Crank  shaft  and  belt  driving,  262 
Crank  shaft  and  direct  driving,  262 
Crank  shaft,  governors  on  end  of,  269 
Crank  shaft  and  piston  rod,  260 
Crank  shaft  and  rope  driving,  262 
Crank  shaft,  source  of  power,  261 
Crank  shaft,  use  of,  260 
Crank  shaft,  steam  valves  worked  from, 

262 

Crank  shaft  works  eccentrics,  262 
Cranks,  and  three-cylinder  engines,  261 
Critical  speed  of  De  Laval  turbine  303 
Critical  temperature  of  steam,  23 
Critical  temperature  of  water  with  in- 
jector, 178 
Criton  softener,  measurements  of  reagents 

in,  184 
Criton  water  softener,  construction  of, 

184 

Criton  water  softener,  filter  in,  185 
Criton  water  softener,  operation  of,  185 
Criton  water  softener,  reagents  used  in, 

184 

Criton  water  softener,  settling  tank,  185 
Crompton's  thermo-electric  pyrometer,  8 
Crosby  steam-engine  indicator,  270 
Cross  compound  condensing  engine,  hori- 
zontal, 224 

Curtis  turbine,  arrangement  of,  311 
Curtis  turbine,  bearings  of,  311 
Curtis  turbine,  construction  of,  309 
Curtis  turbine,  course  of  steam  in,  310 
Curtis  turbine,  electric  controller  with, 

311 

Curtis  turbine,  form  of,  311 
Curtis  turbine,  governor  of,  311 
Curtis  turbine,  lubrication  of,  311 
Curtis  turbine,  separate  stages  in,  309 
Curtis  turbo  generator,  test  of,  313 
Curved  surfaces,  reflection  by,  3 
Gut  off  with  steam  engines,  214 
Cyclone  coal  dust  burning  apparatus,  111 
Cylinder,  air,  Willans  engine,  233 
Cylinders,  arrangement  of  triple-expan- 
sion, WiUans,  234 

Cylinders  of  compound  engines,  Willans 
engine,  234 


INDEX 


389 


Cylinder  condensation  with  expansive 
working,  215 

Cylinder  condensation,  methods  of  curing, 
217 

Cylinders,  proportion  of,  in  triple-expan- 
sion engines,  226 

Cylinders,  steam,  warming,  on  starting 
up,  243 

Cylinders  in  triple-expansion  engines,  226 

Cylinder  walls,  temperature  with  expan- 
sive working,  217 


D 


Dampers,  boiler  flue,  148 

Damper  regulators,  automatic,  149 

Damper  regulator,  Lagonda,  149 

Damper  regulator,  Locke's,  150 

"  Daring "   type  boiler,  construction  of, 

101 
"  Daring  "  type  boiler,  course-of  hot  gases 

in,  102 

"  Daring  "  type  boiler,  drums  in,  102 
"Daring"      type      Thornycroft-Schultz 

boiler,  101 

Davey-Paxman  boilers,  headers  in,  91 
Davey-Paxman  boiler,  mud  drum,  91 
Davey-Paxman  joint,  boiler  flues,  64 
Davey-Paxman  multitubular  boiler,  72 
Davey-Paxman's  water-tube  boiler,  91 
Davies  and  Metcalfe's  injector,  176 
Davis-Perrett  apparatus,  sizes  of,  199 
Davis-Perrett's  electrical  emulsifier,  198 
Dead  points  of  a  crank,  261 
Dead-weight  safety  valve,  154 
Decreased  pressure,    increase    of  latent 

heat,  23 

Definition  of  absolute  pressure,  22 
Definition  of  British  thermal  unit,  13 
Definition  of  gauge 'pressure,  22 
Definition  of  specific  heat,  13 
Degree  of  hardness,  explanation  of,  180 
Degrees  of  humidity  of  air,  28 
Degree  of  superheat,  200 
De  Laval  turbine,  condenser  for  use  with, 

309 

De  Laval  turbine,  construction  of,  301 
De  Laval  turbine,  consumption  of  steam, 

302 

De  Laval  turbine,  critical  speed,  303 
De  Laval  turbine  disc,  velocity  of  steam 

impinging  on,  302 
De  Laval  turbine,  expansion  of  steam  in, 

301 

De  Laval  turbine,  flexible  shaft  in,  303 
De  Laval  turbine,  gearing  of,  305 
De  Laval  turbine,  government  of,  303 
De  Laval  turbine,  nozzles  in,  301 
De  Laval  turbine  pumps,  tests  of,  308 


De  Laval  turbine,  settling  of  the  wheel, 

303 

De  Laval  turbine,  speeds  of,  305 
De  Laval  turbines,  tests  of  at  different 

loads,  308 
De  Laval  turbine,  transmitting  power, 

305 

De  Laval  turbine  wheel,  speed  of,  302 
j   Deposit  on  economizer  tubes,  159 
Deposit  of  salts  in  economizer  tubes,  160 
Description  of  calorimeters,  44 
Description  of  coal,  39 
Description  of  compound  engines,  221 
Description  of  Cornish  boilers,  55 
Description  of  Cornish  valves,  250 
Description  of   double-cylinder  engines, 

220 

Description  of  eccentrics,  246 
Description  of  Lancashire  boilers,  55 
Description  of  peat,  40 
Description  of  slide  valve,  243 
Description  of  steam  boiler,  53 
Description  of  Wheelock  valve,  242 
Desrumaux  water  softener,  construction 

of,  190 
Desrumaux  water  softener,  operation  of, 

191 
Desrumaux    water    softener,    revolving 

wheels  in,  190 

Detroit  boiler,  construction  of,  95 
Detroit  water-tube  boiler,  95 
Dew,  formation  of,  31 
Diagrams,  Bristol's  thermo-electric  pyro- 
meter, 9 
Diagrams,    Crompton's     thermo-electric 

pyrometer,  8 

Diaphragms  in  Bateau  turbine,  316 
Differences  between  coals,  42 
Difference    in    construction    of    econo- 
mizers, 161 
Difference  between  expansion  and  throttle 

governing,  268 
Difference  between  pressure  and  impulse 

turbines,  291 
Difference  of  temperature  and  efficiency 

of  boiler,  37 
Difference  of  temperature  and  efficiency 

of  plant,  37 
Difference  betweem  water-  and  fire-tube 

boilers,  77 
Difficulties  of  lubrication  of  high-speed 

engines,  240 

Direct  driving  and  crank  shaft,  262 
Disadvantages  of  multitubular  boilers,  71 
Dissolved  substances  and  boiling-point  of 

water,  21 
Dissolved  substances  and  freezing-point 

of  water,  21 

Distilled  water  and  exhaust  from  tur- 
bines, 329 


39° 


INDEX 


Distributing  valves  of  high-speed  engines, 

231 

Distributing  valve,  Willans  engine,  232 
Distribution  of  steam  by  pipes,  273 
Dividing  up  cylinders  for  expansion,  217 
Division  of  load  between  ropes,  264 
Domestic  fire-grate,  cause  of  waste,  54 
Domestic  fire-grate,  combustion  in,  53 
Domestic  fire-grate,  waste  of  heat  in,  54 
Domestic  tea  kettle,  55 
Domestic  thermometer,  5 
Donkey  boiler  for  feed  pumps,  172 
Doors  of  boiler  furnaces,  108 
Double-acting  Bumsted  engine,  237 
Double  belt,  formula  for,  264 
Double-cylinder  engines  and  cranks,  261 
Double-cylinder  engines  described,  220 
Double  ported  slide  valve,  construction 

of,  245 
Double-ported  slide  valve,  operation  of, 

245 

Double  tubes  in  surface  condenser,  337 
Doulton's  water  softener,   construction 

of,  188 
Doulton's  water  softener,  operation  of, 

189 

Drainage  of  steam  pipes,  278 
Draught  in  burning  towns  refuse,  114 
Draught,  fan,  and  cooling  towers,  375 
Draught,  forced,  explanation  of,  139 
Draught,  regulation  of,  with  economizers, 

162 
Draught,   pressure    of    air    creating,  in 

boiler  furnace,  28 
Dried  manure  as  fuel,  46 
Drilling  boiler  shells,  61 
Driving  early  Cornish  purnps,  260 
Driving  expansion  governor,  268 
Driving  pulley  of  Lanes,  mill  engines, 

241 

Driving  ropes  of  Lanes,  mill  engines,  241 
Driving  side  of  belt,  263 
Drop  valves,  242,  249 
Drop  valves,  operation  of,  249 
Drop  valves,  piston,  250 
Drop  valves,  tripping  gear  for,  249 
Druitt  Halpin's  thermal  storage,  327 
Drums  in  Atlas  boiler,  93 
Drums  in  "  Daring  "  type  boiler,  102 
Drums  in  Sinclair  boiler,  96 
Drums  of  Stirling  boiler,  86 
Drums  in  Suckling  boiler,  96 
Drums  in  Thornycroft-Schultz  boiler,  100 
Dry  air  pump  for  condenser,  365 
Dry  air  pumps,  two  stage,  365 
Dry  air  as  a  thermal  insulator,  12 
Dry-back  boiler,  72 
Dry-back  boiler,  construction  of,  74 
Dry  steam  and  lubrication,  231 
Dulong's  formula  for  calorific  value,  39 


Duplicate  cooling  towers,  380 

Dust  coal  burning  apparatus,  110 

Dust  settling  apparatus,  towns'  refuse,  114 


E 


Early  forms  of  steam  engines,  214 
Eaves'  dead- weight  safety  valve,  155 
Eccentrics,  description  of,  246 
Eccentrics  and  expansion  governors,  246 
Eccentrics  and  link  motion,  247 
Eccentrics  and  slide  valve,  246 
Eccentric,   operation  of,  when  working 

expansively,  247 

Eccentrics  for  reversing  engine,  247 
Eccentric  rod  and  Corliss  valve,  252 
Eccentrics  worked  from  crank  shaft,  262 
Economic  boiler,  construction  of,  74 
Economizers,  care  of,  in  frosty  weather, 

162 

Economizer  chamber  and  air,  163 
Economizers,  construction  of,  158 
Economizer,  course  of  gases  and  water, 

160 
Economizers,  difference  in  construction 

of,  161 
Economizer,    Green's,    arrangement    of, 

160 
Economizer,  Green's,  capacity  of  tubes, 

160 
Economizer,  heat  taken  out  of  gases  in, 

161 

Economizers,  heating  air  by,  162 
Economizers,  regulation  of  draught  with, 

162 

Economizer,   temperature   of  water   de- 
livered to,  161 
Economizer  tubes,  cleaning  deposit  from, 

159 

Economizer  tubes,  deposit  on,  159 
Economizer  tubes,  deposit  of  salts  in, 

160 

Economizer  tubes,  scrapers  for,  159 
Economy  of  air-  and  water-heating  econo- 
mizers, 162 
Economy  claimed  with  Ellis  &   Eaves 

apparatus,  145 
Economy  of  condensing  with   different 

steam  pressures,  367 
Economy  of  forced  draught,  141 
Edwards  air  pump,  form  of  bucket  in, 

I   Edwards  air  pump,  operation  of,  366 
:   Effect  of  air  in  surface  condenser,  332 
I   Effect  of  ash  on  calorific  value,  41 
,   Effect  of  initial  temperature  on  cooling 

water,  358 
i   Effect  of  nitrogen  on  calorific  value,  41 


INDEX 


Effect  of  oxygen  on  calorific  value  in 

fuels,  38 
Effect  of  pressure  on  surface  of  liquid 

on  boiling-point,  19 

Effect  of  scale  upon  boiler  working,  181 
Effect  of  seasons  upon  chimney  draught, 

135 

Effect  of  temperature  of  water  on  in- 
jector, 178 

Effect  of  tension  of  water  vapour,  31 
Effect  of  water  vapour  in  air  on  boiler 

furnace,  27 
Effective  area  of  chimneys,  formula  for, 

135 
Effective  pressure,  mean,  in  steam  engines, 

215 
Effective  pressures  with  varying  cut-offs, 

compared,  215 
Efficiency  of  belt  drive,  265 
Efficiency   of    boiler  and  difference    of 

temperature,  37 
Efficiency  of  chimneys,  131 
Efficiency  of  condenser,  Prof.  Weighton, 

361 

Efficiency  of  engine  explained,  220 
Efficiency  and  leakage  of  heat,  37 
Efficiency  of  plant  and  difference  of  tem- 
perature, 37 

Efficiency  of  rope  drive,  265 
Efficiency  of  spur  gearing,  265 
Efficiency  of  worm  gearing,  265 
Egg-shaped  Lanes,  boilers,  62 
Ejector  condenser,  advantages  of,  344 
Ejector  condenser,  arrangement  of  steam 

and  water  pipes,  344 
Ejector  condenser,  Ledward,  343 
Ejector  condenser,  operation  of,  343 
Elbows,  loss  of  steam  pressure  in,  275 
Electric  controller  with  Curtis  turbine, 

311 
Electric  governor  for  Parsons  turbine, 

297 
Electric  motor  and  pump  for  condenser, 

363 

Electrical  distribution  and  steam  com- 
pared, 273 

Electrical  emulsifier,  Davis-Perrett,  198 
Electrically   driven    boiler-feed    pumps, 

172 
Electrically  driven  feed  pumps,  objection 

to,  172 
Electricity      generators,      engines      for 

driving,  239 

Electrolytic  action  in  boilers,  181 
Ellis*  and  Eaves  air  heating  with  induced 

draught,  143 
Ellis  and  Eaves  apparatus,  course  of  air 

in,  145 
Ellis    and    Eaves    apparatus,    economy 

claimed  with,  145 


Ellis  and  Eaves  apparatus,  temperature 

of  air,  145 
Emergency  governor  in  Zoelly  turbine, 

329 
Employment  of  fan  with  forced  draught, 

140 

Emulsifier,  electrical,  Davis-Perrett,  198 
Enclosed  feed-water  heaters,  construction 

of,  163 
Enclosed  surface  condenser,  construction 

of,  331 

Enclosure  of  high-speed  engines,  228 
Ends  of  Cornish  boilers,  62 
Ends  of  Lanes,  boilers,  62 
End  thrust  in  turbine,  294 
Energy,  kinetic,  conversion  from  poten- 
tial, 289 

Energy,  kinetic  and  potential,  289 
Energy,  loss  of  in  chimneys,  131 
Engine,  central  valve,  Willans,  232 
Engine,  compound,  proportion  of  cylin- 
ders in,  221 

Engine  governor,  construction  of,  265 
Engine,  high-speed,  Bumsted,  236 
Engine,  Peache,  course  of  steam  in,  238 
Engine,  Peache,  valves  of,  237 
Engine,  reversing,  by  eccentrics,  247 
Engine,  steam,  reciprocating,  213 
Engine,  steam,  work  will  perform,  218 
Engines,  Belliss,  construction  of,  229 
Engines,   Brotherhood,  construction   of, 

229 

Engines,  Browett,  construction  of,  229 
Engines,  compound,  described,  221 
Engines,    compound,   vertical,    arrange- 
ment of,  239 

Engines,  double-cylinder,  described,  220 
Engines     for     driving    compressed    air 

machinery,  239 
Engines  for  driving  electricity  generators, 

229 

Engines,  government  of,  265 
Engines,  high-speed,  227 
Engines,  intermediate-speed,  227 
Engines,  low-speed,  227 
Engines,  mill,  Lanes.,  240 
Engines,  piston  speed  of,  227 
Engines,  pumping,  Cornish,  213 
Engines,  quadruple  expansion,  227 
Engines,  quickly  revolving,  228 
Engines,  reciprocating  valves  for,  242 
Engines,  steam,  early  forms,  214 
Engines,  steam,  expansive  working  with, 

214 

Engines,    steam,    working    without    ex- 
pansion, 214 

Engines,  triple-expansion,  226 
Engines,  twin-cylinder,  arrangement  of, 

239 
Engines,  use  of  flywheels  with,  239 


392 


INDEX 


Engines,  vertical  and  horizontal,  239 
Entropy,  explanation  of,  9 
Enumeration  of  boiler  fittings,  151 
Erith  underfed  mechanical  stoker,  126 
Ether  and  heat,  2 
Ether  all  pervading,  2 
Ether  and  planetary  space,  2 
Ether,  what  it  is,  1 

Euston  steam  trap,  construction  of,  286 
Evaporation  from  cooling  ponds,  369 
Evaporation    and    humidity   of    atmo- 
sphere, 335 

Evaporation  from  spraying  nozzles,  370 
Evaporation,  variation  of,  with  weather, 

369 
Evaporation  of  water,  cooling  effect  of, 

335 

Evaporation,  water  lost  by,  335 
Evaporative  condenser,  Eraser,  335 
Evaporative  condenser,  water  used  with, 

335 

Evaporative  surface  condenser,  construc- 
tion of,  334 
Evaporator,    Central    Engineering    Co., 

205 

Evaporators,  construction  of,  205 
Evaporators,  Royle,  205 
Evaporators,  use  of,  205 
Evaporators,  Weir,  205 
Exhaust  and  live  steam,  combination  of, 

for  turbines,  325 
Exhaust  from  turbines  and  boiler  feed, 

329 
Exhaust    from    turbines    and    distilled 

water,  329 
Exhaust  steam,  adaptability  for  turbines, 

323 
Exhaust  steam   for  feed- water  heaters, 

164 

Exhaust  steam  and  injector,  175 
Exhaust  steam,  storage  of,  for  turbines, 

324 
Exhaust  steam,  turbines  working  with, 

322 

Exhaust  steam  and  Zoelly  turbine,  323 
Expansion  bends  in  steam  pipes,  279 
Expansion  of  bodies  with  heat,  16 
Expansion  of  brass  and  iron,  6 
Expansion  and  contraction  of  air  with 

temperature,  25 
Expansion    and    contraction    of    steam 

pipes,  279 

Expansion,  division  of  cylinders  for,  217 
Expansion  governor,  construction  of,  267 
Expansion  governor,  driving,  268 
Expansion  governors  and  eccentrics,  246 
Expansion  governor,  operation  of,  267 
Expansion  governor,   Wilson   Hartnell, 

267 
Expansion  pyrometer,  6 


Expansion,  quadruple  engines,  227 
Expansion  of  steam  adibiatically,  290 
Expansion  of  steam  in  De  Laval  turbine, 

301 
Expansion  of  steam  for  velocity  turbine, 

290 

Expansion  and  throttle  governing,  dif- 
ference between,  268 
Expansion,  triple  engines,  226 
Expansion  of  water  in  freezing,  16 
Expansive  working  and    cylinder    con- 
densation, 215 
Expansive    working  in    steam  engines, 

214 
Expansive     working,     temperature     of 

cylinder  walls  with,  217 
Expansive  working  and  water  vapour, 

217 
Experiments,  condenser,  Richard  Allen, 

352 
Experiments      on      condensers,      Prof. 

Weighton,  360 

External  furnaces,  Cornish  boilers,  69 
External  furnaces,  Lancashire  boilers,  69 


Fahrenheit  scale,  4 

Fan,    arrangement     of,    with     induced 

draught,  141 

Fan  centrifugal,  construction  of,  146 
Fans  for  mechanical  draught,  145 
Fan,  power  required  to  drive,  147 
Fan,  propeller,  use  of,  146 
Fan  draught  and  cooling  towers,  375 
Feed  of  underfeed  mechanical  stokers, 

126 

Feeding  mechanical  stokers,  118 
Feed-pumps  and  donkey  boiler,  172 
Feed-water  heaters  and  air  vessels,  169 
Feed-water  heater,  Climax  boiler,  99 
Feed-water  heaters  and  exhaust  steam, 

164 

Feed-water  heaters  and  live  steam,  164 
Feed-water  heater,  live  steam,   Holden 

&  Brooke,  166 

Feed-water  heaters,  open  steam,  arrange- 
ment of,  168 

Feed-water  heater  as  purifier,  167 
Feed-water  heater,  Royle,  166 
Feed  water  in  Atlas  boiler,  93 
Feed  water  in  Stirling  boiler,  86 
Feed  water,  matter  contained  in,  Prof. 

Thurston's  estimate,  179 
Feed  water,  methods  of  removing  foreign 

bodies  from,  181 
Feed    water,    objection     to     condensed 

water  for,  169 
Feed- water  pumps,  forms  of,  170 


INDEX 


393 


Feed  water  purifying,  179 
Feed-water  regulators,  178-' 
Feed  water,  substances  contained  in,  179 
Feed  water,  temperature  obtainable  with 

exhaust  steam,  166 
Feed  water,  use  of  hot  gases  for,  156 
Ferranti-Hopkinson  stop-valve,  257 
Filter  cleaning  in  Eeisert  water  softener, 

188 
Filter  in  Bruun-Lowener  water  softener, 

188 

Filter  in  Criton  water  softener,  185 
Filters  and  water  softeners,  183 
Finely  divided  charcoal,  properties   of, 

13 
Finely  divided  substances  in  water  and 

boiling-point,  21 

Finely  divided  substances,  thermal  con- 
ductivity, 12 

Fire  bars  in  Auto  stoker,  123 
Fire  bars,  interlocking,  Meldrum,  115 
Fire    bars,    movement    of,    in    Vickers 

stoker,  123 

Fire  bar,  rocking,  Neemes,  110 
Fire  bars,  rocking,  Neil,  108 
Fire  bars,  water-tube  boilers,  82 
Fire  grate,  Neil,  109 
Firing  Cornish  boilers,  69 
Firing  Lanes,  boilers,  69 
Fire-tube  boilers,  description  of,  55 
Flash  point  of  liquid  fuels,  47 
Fletcher's  oil  separator,  construction  of, 

194 

Flexible  shaft  in  De  Laval  turbine,  303 
Flow  of  steam  through  pipes,  table  of, 

276,  277 

Flow  of  water  in  injector,  175 
Flue  dampers,  operation  of,  148 
Flues  of  Cornish  boilers,  56 
Flues  of  Lancashire  boilers,  56 
Flue  gases,  object  of  testing,  205 
Flue  gases,  percentage  of  C02  and  loss  of 

fuel,  207 

Flue  gas  testers,  principle  of,  207 
Flue  gas  testing  apparatus,  Orsat,  212 
Flywheel  speeds  of  high  and  low  speed 

engines,  228  « 

Flywheels,  use  of,  with  engines,  239 
Forced  draught,  air  required  with,  141 
Forced  draught,  with  air  heating,  139 
Forced  draught,  closed  ashpit  system,  139 
Forced  draught,  closed  fire-room  system, 

139 

Forced  draught,  cost  of  producing,  141 
Forced  draught,  economy  with,  141 
Forced  draught,  explanation  of,  139 
Forced  draught,  higher  pressure  obtained 

with,  140 
Forced  draught,   temperature   of    gases 

with,  140 


Formula  for  calorific  value,  Dulong,  39 

Formula  of  Carnot's  law,  36 

Formula  for  converting   Centigrade  to 

Fahrenheit,  5 
Formula  for  cooling  water  required  with 

condensers,  351 
Formula  for  double  belt,  264 
Formula  for  effective  area  of  chimney, 

135 

Formula  for  Fahrenheit  to  Centigrade,  5 
Formula  for  Green's  economizer,  160 
Formula  for  horse-power  of  steam  engine, 

218 
Formulae  for  loss  of  pressure  in  steam 

pipes,  274 

Formula  for  power  to  move  air,  147 
Formula  for  pressure  in  boilers,  80 
Formula  for  rate  of  transmission  of  heat, 

12 

Formula  for  size  of  belt,  263 
Formula  for  sizes  of  rope,  265 
Formula  for  velocity  of  gases  in  chimney, 

133 
Formula  for  volume  and  pressure  of  gas, 

289 

Foundations  of  chimneys,  138 
Foundations  for  Lanes,  mill  engines,  241 
Fraser  and  Chalmers  compound  Cornish 

boiler,  76 
Fraser's  condenser,  advantages  claimed 

for,  336 

Fraser's  evaporative  condenser,  335 
Freezing-point  on  Centigrade  scale,  4 
Freezing-point  on  Fahrenheit  scale,  4 
Freezing-point  on  Reaumur  scale,  4 
Freezing-point  of    water    and   dissolved 

substances,  21 

Friction  of  slide  valve  on  cylinder,  248 
Friction  of  steam  in  pipes,  heat  generated 

by,  274 

Fuel,  air  required  for  combustion  of,  130 
Fuel,  approximate  analysis  of,  43 
Fuel,  dried  manure,  46 
Fuel,  gaseous,  49 

Fuel,  liquid,  burning  apparatus,  111 
Fuel,  loss  of,  and  percentage  of  C02,  207 
Fuel,  saw-dust,  46 
Fuel,  ultimate  analysis  of,  43 
Furnace  bars,  special  forms  of,  108 
Furnaces,  boiler,  doors  of,  108 
Furnace,  combustion  of  fuel,  37 
Furnace  draught  by  steam  jets,  147 
Furnace  gases,  course  of,  in  locomotive 

boiler,  73 
Furnace    gases,    course    of,    in    marine 

boiler,  74 

Furnace  gases,   splitting  up,  in  multi- 
tubular  boilers,  71 
Furnace  grates,  Cornish  boilers,  107 
Furnace  grates  in  Lanes,  boilers,  107 


394 


INDEX 


Furnace  grates,  marine  boilers,  107 
Furnace  grates,  water-tube  boilers,  107 
Furnaces  of  Lanes,  boilers,  56 
Furnace,  methods  of  providing  air  for, 

127 

Furnace  in  Nesdrum  boiler,  87 
Furnace  of  Stirling  boiler,  84 
Furnace  of  Woodeson  boiler,  88 
Furnace  ventilation  in  mines,  127 
Furnace  ventilation,  motive  column  for, 

128 


G 


Galloway  boiler  for  burning  refuse,  70 

Galloway  boiler,  construction  of,  70 

Galloway  cone  tubes,  description  of,  59 

Galloway  cone  tube,  early  form,  60 

Galloway  cone  tube,  modern  form,  60 

Galloway  superheater,  203 

Galloway  water-tube  boiler,  93 

Galvanized  iron  mats  in  cooling  towers, 
377 

Gas,  solution  of,  in  water,  33 

Gas  tar,  calorific  value  of,  48 

Gas' tar,  composition  of,  48 

Gas  tar  as  fuel,  48 

Gas  tar,  production  of,  48 

Gases  in  atmosphere,  18 

Gases  found  in  collieries,  description  of,  52 

Gases,  specific  heats  of,  14,  30 

Gases,  volume  of,  produced  by  com- 
bustion, 130 

Gases  and  water,  course  of,  in  economizer, 
160 

Gaseous  condition,  17 

Gaseous  fuel,  49 

Gauge  cocks,  explanation  of,  151 

Gauge  pressure,  definition  of,  22 

Gearing  of  De  Laval  turbine,  305 

Giving  motion  to  the  slide  valve,  246 

Globe  stop  valves,  255 

Governor,  control  of  steam  supply  by, 

Governor  of  Curtis  turbine,  311 
Governors  on  end  of  crank-shaft,  269 
Governor  of  Hamilton  Holzwarth  tur- 
bine, 321 

Governors  of  high-speed  engines,  231 
Governor  of  Parsons  turbine,  296 
Governor  of  Peache  engine,  239 
Governor,  Pickering,  265 
Governor  of  Rateau  turbine,  316 
Governor  of  steam  engine,  use  of,  242 
Governor  and  stop  valve,  255 
Governor  of  Willans  engine,  235 
Governor  of  Zoelly  turbine,  320 
Government  of  De  Laval  turbine,  303 
Government  of  engines,  265 


Gradation  of  coals,  41 

Grate  area  of  furnace  required,  132 

Grate  area,  proportion  to  chimney,  132 

Grate  bars  of  over-feed  stokers,  120 

Grate  bars,  Neil,  109 

Great  Calorie,  14 

Green's  economizer,  arrangement  of,  160 

Green's  economizer,  formula  for,  160 

Guttmann  water  softener,   construction 

of,  188 
Guttmann  water  softener,  operation  of, 

188 


H 


Halpin,  Druitt,  thermal  storage,  327 

Hamilton  Holzwarth  turbine,  bearings 
of,  321 

Hamilton  Holzwarth  turbine,  construc- 
tion of,  321 

Hamilton  Holzwarth  turbine,  governor 
of,  321 

Hamilton  Holzwarth  turbine,  lubrication 
of,  321 

Hard  water,  explanation  of,  180 

Hardwick  feed- water  heater,  164 

Harris-Anderson  apparatus,  course  of 
water  and  re-agents  in,  193 

Harris-Anderson  apparatus  for  removing 
oil,  198 

Harris-Anderson  water  softener,  con- 
struction of,  192 

Harris-Anderson  water  softener,  mixing 
tubes,  192 

Harris-Anderson  water  softener,  opera- 
tion of,  192 

Harris-Anderson  water  softener,  treat- 
ment vessels,  192 

Headers  in  Atlas  boiler,  93 

Headers  in  Babcock  boiler,  83 

Headers  in  Davey-Paxman  boiler,  91 

Headers  in  Wood  boiler,  92 

Heat  absorbed  by  cooling  water,  333 

Heat  absorption  and  Prof.  Tyndal,  11 

Heat  applied  to  bi-carbonates,  33 

Heat  in  compressed  air,  Willans  engine, 
234 

Heat  conduction  and  air,  10 

Heat  conduction  and  metals,  10 

Heat  contained  in  the  earth,  2 

Heat  and  convection,  9 

Heat  engines,  Carnot's  law,  36 

Heat  and  expansion  of  bodies,  16 

Heat  from  other  planets,  2 

Heat  from  the  sun,  2 

Heat  generated  by  friction  of  steam  in 
pipes,  274 

Heat  liberated  by  carbon-forming  car- 
bonic oxide,  38 


INDEX 


395 


Heat  liberated  by  solution    of    gas    in 

water,  33 

Heat  liberated,  formation  of  S02,  38 
Heat  liberated  in  forming  carbonic  acid, 

38 
Heat  liberated  when  hydrogen  combines 

with  oxygen,  38 
Heat  radiation,  9 
Heat  rays  from  a  black  body,  3 
Heat  rays  reflected,  3 
Heat  taken  out  of  gases  in  economizer, 

161 

Heat,  theory  of,  1 
Heat,  transmission,  9 
Heat  waves,  lengths  of,  2 
Heat  waves,  properties  of,  2 
Heat,  what  it  is,  1 
Heating  air  by  economizers,  162 
Heating  of  belt  pulleys,  263 
Heating  curves  with  plain  and  corrugated 

tubes,  Wainwright,  167 
Heating  feed- water  for  boilers,  156 
Heating   of  water  in    Bruun    Lowener 

water-softener,  188 

Height  of  chimney  cooling  towers,  375 
Height    of    chimney    and    intensity    of 

draught,  137 
Height  of  chimney  and  velocity  of  gases, 

133 

Height  of  chimneys,  Kent's  table  for,  135 
Heine  boiler,  construction  of,  95 
Heine  water-tube  boiler,  95 
Henderson  mechanical  stoker,  119 
High-  and  low-speed  engines,  piston  speed 

of,  228 
High  latent  heat,  effect  on  size  of  steam 

engines,  23 

High  pressure  and  Lanes,  boilers,  80 
High  pressures,  strain  on  boiler  shell,  80 
High-speed  engine,  Bumsted,  236 
High-speed  engines,  difficulties  of  lubri- 
cating, 240 
High-speed   engines,  distributing  valves 

of,  231 

High-speed  engines,  enclosure  of,  228 
High-speed  engines,  governors  of,  231 
High-speed  engines,  iron  used  in,  231 
High-speed  engines,  lubricant  of,  231 
High-speed  engines,  lubrication  of,  228 
High-speed  engines,  lubrication  working 

out  from,  240 

High-speed  engines,  oil  pumps  for,  232 
High-speed  engine,   Scott  &   Mountain, 

construction  of,  232 
High  vacua  and  cooling  water,  351 
High- water  safety  apparatus,  155 
Higher  pressure    obtained  with   forced 

draught,  140 

Highest  efficiency  speed,  De  Laval  tur- 
bine, 302 


Hodgkinson  mechanical  stoker,  122 

Holden  &  Brooke's  feed- water  heater  for 
live  steam,  166 

Holden  &  Brooke's  injectors,  176 

Holden  liquid  fuel  apparatus,  arrange- 
ment of,  112 

Hopkinson  central  pressure  stop  valve, 
257 

Hopkinson  central  pressure  valve,  con- 
struction of,  257 

Hopkinson-Ferranti  stop  valve,  257 

Hopkinson's  parallel-slide  stop  valve,  256 

Hopkinson  stop  valve,  central  pressure, 
257 

Hoppes  feed-water  heater  and  purifier, 
168 

Horizontal  compound  engines,  arrange- 
ment of,  239 

Horizontal  cross-compound  condensing 
engine,  224 

Horizontal  engine  and  vertical  boiler,  223 

Horizontal  tandem  compound  condensing 
engine,  224 

Horizontal  tandem  compound  engine,  223 

Horizontal  triple-expansion  condensing 
mill  engine,  240 

Horizontal  triple  -  expansion  engines, 
arrangement  of,  239 

Horizontal  and  vertical  engines,  239 

Horse-power,  15 

Horse-power  of  boilers  discussed,  132 

Horse-power,  brake,  measurement  of,  220 

Horse-power  and  the  British  thermal 
unit,  15 

Horse-power  of  engine  with  multiple 
cylinders,  320 

Horse-power,  indicated,  219 

Horse-power  of  steam  engine,  formula 
for,  218 

Hot  gases  in  chimney,  pressure  of,  133 

Hot  gases,  course  of,  in  Atlas  boiler,  94 

Hot  gases,  course  of,  in  Nesdrum  boiler, 
87 

Hot  gases,  course  of,  in  Stirling  boiler,  84 

Hot  gases,  course  of,  with  forced  draught, 
140 

Hot  gases,  limit  to  use  of,  for  feed-water 
heating,  158 

Hot  gases,  limiting  temperature  in  chim- 
ney, 129 

Hot  gases,  passage  of,  in  Cornish  boilers, 
56 

Hot  gases,  passage  of,  in  Lanes,  boilers, 
56 

Hot  gases,  temperature  of,  in  boiler 
furnace,  131 

How  power  is  transmitted  by  belt,  262 

Humidity  of  air,  degrees  of,  28 

Humidity  of  atmosphere  and  evaporation, 
35 


396 


INDEX 


Button's  table  of  pressures  for  different 

fuels,  130 

Hydrogen  in  atmosphere,  18 
Hydrogen  combining  with  oxygen,  heat 

liberated,  38 


Ignition  point  of  liquid  fuels,  48 

I.H.P.  and  cooling  surface  in  condenser, 

352 

Importance  of  circulation  in  boilers,  54 
Importance  of  mixing  reagents  in  water 

softeners,  182 

Impurities  in  water  and  priming,  34 
Inches  and  pounds,  vacuum  in,  332 
Incidence,  angle  of,  4 
Inclination  of  steam  pipes,  278 
Increase  of    boiling    temperature    with 

pressure,  21 
Increase  of  efficiency  of  steam  turbine  by 

increased  vacuum,  37 
Increase  of  pressure  on  surface  of  liquid, 

19 
Increase  of  velocity  of  steam  in  De  Laval 

turbine,  301 
Increase  of  velocity  of  steam  with  lowered 

pressure,  291 
Increased    pressure,   decrease  of    latent 

heat,  23 

Indicated  horse  power,  219 
Indications  of  the  barometer  explained, 

19 

Indicator  cards,  atmospheric  line  on,  272 
Indicator  cards,  planimeter  for,  272 
Indicator  cards,  pressures  shown  on,  272 
Indicator  cards  from  steam  engine,  271 
Indicator  for  steam  engine,  219 
Indicator,   steam  engine,   operation  of, 

271 

Induced  draught,  advantages  of,  143 
Induced  draught  and  air  heating,  143 
Induced  draught  and  air  leakage,  143 
Induced    draught,  arrangement    of  fan 

with,  141 
Induced  draught,  course  of  gases  and  air 

with,  142 

Induced  draught,  explanation  of,  141 
Induced  draught,  power  required  with, 

142 
Induced  draught,  volume  of  gases  with, 

142 

Infra  red  rays,  3 
Initial  temperature  and  cooling  water, 

358 
Initial  temperature  and  cooling  water 

required,  351 

Injector,  construction  of,  174 
Injector    and     critical    temperature    of 

water,  178 


steam,  175 


Injector,  Davies  &  Metcalfe,  176 
Injector,  effect  of  temperature  of  water 

on,  178 

Injector  with  exhaust  steam,  175 
Injector,  flow  of  water  in,  175 
Injectors,  Holden  &  Brooke's,  176 
Injector  lift  and  quantity,  177 
Injector  with  live  and  exhaust  s 
Injector,  operation  of,  174 
Injector,  pipes  connected  to,  175 
Injector,  pressure,  can  work  against,  174 
Injector,  principle  of,  173 
Injector,  quantity  of  water  delivered  bv, 

176 

Injector,  supply  of  water  for,  177 
Injector,  temperature  of  feed  with,  176 
Insulators,  thermal,  11 
Intensity  of  draught  and  height  of  chim- 
ney, 137 

Interlocking  fire  bars,  Meldrum,  115 
Intermediate-speed  engines,  227 
Intermediate  turbines,  289 
Invisible  heat  rays,  3 
Iron  for  cooling  towers,  379 
Iron  plates  in  cooling  towers,  377 
Iron  used  in  high-speed  engines,  231 
Iron-work  for  water  tube  boilers,  78 


Jacketing  steam  cylinders  for  condensa- 
tion, 217 

Jet  condenser,  air  pump  for,  340 

Jet  condenser,  Balcke,  340 

Jet  condenser  and  cooling  tower,  340 

Jet  condenser,  Mirrlees  Watson,  341 

Jet  condensers,  parallel  current,  340 

Jet  condenser,  pumps  for,  340 

Jet  condenser  versus  surface  condensers, 
341 

Jet  condenser  with  water  trays,  341 

Jet  condenser,  Worthington,  pump  for, 
343 

Jet  condenser,  Worthington,  velocity  of 
steam  in,  343 

Jet  condenser,  Worthington,  water  jet 
in,  342 

Jointing  rings  for  steam  pipes,  280 

Jointing  of  steam  pipes,  278 

Joints  of  boiler  flues,  63 

Joints  in  boiler  shells,  61 

Joule's  equivalent,  15 


Keeler  rocking  fire  grate,  109 
Kennicott  water  softener,  construction 

of,  189 
Kent's  table  for  the  height  of  chimneys, 

135 


INDEX 


397 


Kinetic  energy,  conversion  from  poten- 
tial energy,  289 

Kinetic  energy  and  potential  energy,  289 

Koppel,  Arthur,  water  softener,  con- 
struction of,  191 

Koppel,  Arthur,  water  softener,  opera- 
tion of,  191 

Koppel,  Arthur,  water  softener,  steam 
heating  apparatus  in,  191 

Korting's  liquid-fuel  burning  apparatus, 
113 


Lagonda  damper  regulator,  149 
Lancaster  steam  trap,  construction  of, 

283 

Lanes,  boilers,  ash  pit,  59 
Lanes,  boilers,  construction  of,  60 
Lanes,  boilers,  description  of,  55 
Lanes,  boilers,  egg  shape,  62 
Lanes,  boilers,  ends  of,  62 
Lanes,  boilers,  external  furnaces,  69 
Lanes,  boilers,  firing,  69 
Lanes,  boiler  flues,  56,  63 
Lanes,  boilers,  furnaces  of,  56 
Lanes,  boilers,  furnace  grates,  107 
Lanes,  boilers  and  high  pressure,  80 
Lanes,  boilers,  hot  gases,  passage  of,  56 
Lanes,  boilers,  mud  hole,  59 
Lanes,  boilers,  radiation  from,  58 
Lanes,  boilers,  setting,  68 
Lanes,  boilers,  sizes  of,  62 
Lanes,  boiler,  Tinker's  superheater  fitted 

to,  201 

Lanes,  boilers,  water  below  furnace,  59 
Lanes,  boilers,  water  in,  58 
Lanes,  cotton  mills  and  cooling  ponds, 

368 
Lanes,  mill  engines,  condensers  fixed  in, 

241 

Lanes,  mill  engine,  driving  pulley  of,  241 
Lanes,  mill  engine,  driving  ropes  of,  241 
Lanes,  mill  engines,  foundations  for,  241 
Lanes,  mill  engines  and  rope  drive,  240 
Lanes,   mill  engines,   speed   of    driving 

ropes,  241 
Lanes,  mill  engines,  Wheelock  expansion 

gear  for,  241 

Lanes,  versus  Cornish  boiler,  60 
Lap  joints,  boiler  shells,  61 
Lap  of  slide  valve,  248 
Largest  diameters  of   vessels  in  water- 
tube  boilers,  81 
Latent  heat,  16 
Latent  heat,  decrease  of,  with  increased 

pressure,  23 

Latent  heat  of  steam,  17 
Latent  heat  and  variation  of  pressure,  22 


Latent  heat  of  water,  17 

Launch  type  Thornycroft  boiler,  102 

Law  of  capacity  of  air  for  water  vapour, 

25 

Law,  Carnot,  heat  engines,  36 
Laws  of  reflection,  3 
Laws  of  refraction,  3 
Law  of  successive  changes  of  heat,  36 
Lead  of  slide  valve,  248 
Leakage  of  heat  and  efficiency,  37 
Leakage  of  steam  and  slide  valve,  247 
Ledward  ejector  condenser,  343 
Length  of  radius  of  crank,  261 
Length  of  turbine,  294 
Lever  safety  valve,  154 
Lift  of  injector  and  quantity,  177 
Lifting  of  water  by  steam  traps,  281 
Light  waves,  lengths  of,  2 
Lignites,  composition  of,  41 
Limit  for   circulating  water   employed 

Prof.  Weighton,  363 
Limiting  temperature  of  cooling  water, 

332 
Limiting  temperature   of  hot   gases  in 

chimney,  129 
Limit  to  use  of  hot  gases  for  feed- water. 

heating,  158 

Link  motion  for  eccentrics,  247 
Link  motion  and  slide  valve,  247 
Liquid  condition,  17 
Liquid  fuels,  46 

Liquid  fuel  apparatus,  Holden,  111 
Liquid  fuel  burning  apparatus,  Korting, 

113 
Liquid  fuel  burning  apparatus,  Marshall, 

112 

Liquid  fuels,  flash  point,  47 
Liquid  fuels,  ignition  point,  48 
Liquids,  specific  heats  of,  13 
Live  steam  and  feed-water  heaters,  164 
Lloyd's,  explanation  of,  68 
Lloyd's  formula  boiler  furnaces,  65 
Locke's  damper  regulator,  150 
Locomotive  boiler,  construction  of,  73 
Loss  of  energy  in  chimneys,  131 
Loss  of  heat  by  radiation  from  steam 

pipes,  275 
Loss  of  pressure  in  steam  pipes,  formulae 

for,  274 

Loss  of  steam  pressure  in  elbows,  275 
Loss  of  steam  pressure  in  valves,  275 
Loss  of  water  in  cooling  towers,  380 
Loss  of  water  with  spraying  nozzles,  370 
Louvre  boards  for  cooling  ponds,  370 
Low  pressures,  high  latent  heat,  23 
Low-speed  engines,  227 
Low  steam  pressures  and  size  of  steam 

engines,  23 

Low-water  safety  apparatus,  155 
Low-water  safety  valve,  155 


398 


INDEX 


Lowered  pressure,  increase  of  velocity  of 

steam  with,  291 

Lubricant  for  high-speed  engines,  231 
Lubrication  of  Bumsted  engine,  236 
Lubrication  of  Curtis  turbine,  311 
Lubrication  and  dry  steam,  231 
Lubrication    of    Hamilton    Holzwarth 

turbine,  321 

Lubrication  of  high-speed  engines,  228 
Lubrication  in  Parsons  turbine,  296 
Lubrication  of  Peache  engine,  237 
Lubrication  and  superheated  steam,  231 
Lubrication  and  superheated  steam  in 

turbines,  328 

Lubrication  of  Willan's  turbine,  300 
Lubrication  working  out  from  high-speed 

engines,  240 


Marine  boiler,  72 

Marine  boiler,  Babcock,  83 

Marine  boiler,  construction  of,  74 

Marine  boilers,  furnace  grates,  107 

Marriott  steam  separators,  construction 

of,  203 

Marshall's  boiler,  steam  drums,  91 
Marshall's  boiler,  water  legs,  91 
Marshall's  liquid  fuel  burning  apparatus, 

112 

Marshall's  water-tube  boiler,  91 
Marshall's  water-tube  boiler,  construc- 
tion of,  91 
Marshall's  water-tube  boiler,  course  of 

hot  gases,  91 

Matter,  three  states  of,  16 
McLeod's  and  Henry's  boiler  brickwork, 

69 

Mean  back  pressure  in  cylinder,  218 
Mean  effective  pressure  explained,  215, 

218 
Mean  effective  pressure  in  steam  engines, 

215 

Mean  pressures,  table  of,  216 
Measurement  of  brake  horse-power,  220 
Measurement    of    reagents    in    Bruun- 

Lowener  water  softener,  187 
Measurements    of    reagents    in    Criton 

softener,  184 
Measurement  of  reagent  in  Reisert  water 

softener,  186 

Measurement  of  ropes,  264 
Measurement  of  temperatures,  5 
Measurement  of  vapour  in  air,  improved 

method,  29 

Measurement  of  wood,  45 
Measuring  percentage  of  water  vapour  in 

air,  28 
Mechanical  draught,  fans  for,  145 


Mechanical    draught,   rates  of  combus- 
tion with,  133 

Mechanical  draught,  sizes  of  fan  for,  146 
Mechanical  equivalent  of  heat  explained, 

15 

Mechanical  stokers,  advantages  of,  115 
Mechanical  stoker,  Bennis,  122 
Mechanical  stokers,  chain  grate,  124 
Mechanical  stokers,  coking,  117 
Mechanical  stokers,  feeding,  118 
Mechanical  stoker,  Henderson,  119 
Mechanical  stoker,  Hodgkinson,  122 
Mechanical  stokers,  overfeed,  117 
Mechanical  stokers,  rate  of  combustion 

with,  117 

Mechanical  stokers,  requirements  of,  115 
Mechanical  stoker,  sprinkler,  118 
Mechanical  stokers  and  steam  jets,  122 
Mechanical  stoker,  underfeed,  Erith,  126 
Mechanical  stokers  underfeed,  feed  of,  126 
Mechanical  stoker,  Underfeed  Stoker  Co., 

126 

Mechanical  stoker,  Wilkinson,  122 
Mechanical  Theory  of  Heat,  1 
Megasse,  calorific  value  of,  45 
Meldrum's  coal-dust  furnace,  110 
Meldrum's  coker  stoker,  119 
Meldrum's  colliery  refuse  destructor,  114 
Meldrum's  furnace  for  colliery  refuse,  70 
Meldrum's  interlocking  fire  bars,  115 
Meldrum's  refuse  destructor  grate,  115 
Meldrum's  steam  jet  furnace  draught, 

147 

Melting  points  of  metals,  6 
Mercurial  barometer,  18 
Mercurial  thermometer  to  800°  P.,  5 
Metals  and  heat  conduction,  10 
Methods  of  curing  cylinder  condensation, 

217 
Methods  of  providing  air  for  the  furnace, 

127 
Methods  of  removing  foreign  bodies  from 

feed  water,  181 

Metropolitan  District  Eailway,  Westing- 
house  turbine,  313 

Midget  steam  trap,  construction  of,  285 
Mill  engines,  Lanes.,  240 
Mirrlees  Watson  jet  condenser,  £41 
Mirror,  reflected  image  in,  3 
Mixing  of  reagents  and  water  in  Bruun- 

Lowener  water  softener,  187 
Mixing  tubes  in  Harris-Anderson  water 

softener,  192 

Modern  form  Galloway  tube,  60 
Modern  practice,  steam  pressures  used, 

36 

Morrison  suspension  boiler  furnace,  65 
Motive  column  and  chimney  draught,  128 
Motive  column  of  furnace  ventilation,  128 
Motive  column,  reasons  for,  128 


INDEX 


399 


Motor  boiler,  Turner-Miesse,  106 
Motor-wagon  boilers,  Thornycroft,  105 
Motor- wagon  boiler,  White,  106 
Mountain  sickness,  20 
Movement  of-fire  bars  in  Vickers  stoker, 

128 

Movement  of  stoker,  grate  bars,  120 
Mud  drum  in  Davey-Paxman  boiler,  91 
Mud  drum  in  Nesdrum  boiler,  88 
Mud  drums  in  Stirling  boiler,  86 
Mud  drums,  use  of  for  removing  foreign 

bodies,  182 

Mud  drums.  Woodeson  boiler,  90 
Mud  hole  in  Lanes,  boilers,  59 
Mud  precipitate  in  Archbutt-Deely  appa- 
ratus, 184 
Multiple  cylinders,  horse-power  of  engine 

with,  220 

Multitubular  boilers,  advantages  of,  71 
Multitubular  boilers,  construction  of,  70 
Multitubular  boiler,  Davey-Paxman,  72 
Multitubular  boilers,  disadvantages  of,  71 
Multitubular  boiler,  forms  of,  72 
Multitubular  and  Cornish  boiler,  76 


N 


Natural  gas,  calorific  value,  52 
Natural  gas,  composition  of,  52 
Natural  gas,  production  of,  51 
Natural  mineral  springs,  32 
Neemes  rocking  fire  bar,  110 
Neil's  fire  grate,  109 
Neil's  rocking  fire  bars,  108 
Nesdrum  boiler,  construction  of,  87 
Nesdrum  boiler,  furnace  in,  87 
Nesdrum  boiler,  hot  gases,  course  of,  87 
Nesdrum  boiler,  mud  drum,  88 
Nesdrum  boiler,  steam  drum,  88 
Nesdrum  boiler,  superheater,  88 
Nesdrum  boiler,  tubes  in,  87 
Nesdrum  boiler,  water  circulation,  88 
Nesdrum  superheater,  202 
Nesdrum  water-tube  boiler,  87 
Nominal  horse-power  explained,  220 
Nozzles  for  cooling  ponds,  369 
Nozzle  in  De  Laval  turbine,  301 
Nozzles,  spraying,  evaporation  from,  370 


0 


Oil  catcher  and  steam  exhaust  head,  197 
Oil  pumps  for  high-speed  engines,  231 
Oil  pumps  in  Parsons  turbine,  296 
Oil  relay  in  Zoelly  turbine  governor,  320 
Oil    removing,    apparatus    for,    Harris- 
Anderson,  198 
Oil  removing,  special  apparatus  for,  197 


Oil  separators,  construction  of,  193 

Oil  separator,  Fletcher,  construction  of, 

194 

Oil  separator,  Reid,  construction  of,  195 
Oil  separator  vacuum,  Cochrane,  195 
Oil  from  water,  removing,  193 
Olefine,  47 
Open  steam  feed-water  heaters,  arrange 

ment  of,  168 

Open  tank  surface  condensers,  338 
Origin  of  petroleum,  46 
Orsat  apparatus,  construction  of,  212 
Orsat  apparatus  for  flue  gas  testing,  212 
Orsat  apparatus,  operation  of,  212 
Overfeed  mechanical  stokers,  117 
Overfeed  stokers,  grate  bars  of,  120 
Overload  valve  in  Zoelly  turbine,  321 
Oxygen  in  atmosphere,  18 
Oxygen,  effect  of  in  calorific  value  in 

fuels,  38 
Oxygen  for  furnace,  effect  of  water  vapour 

in  air,  27 


Paraffin,  47 

Parallel  current  jet  condensers,  340 

Parallel  slide  stop  valve,  advantages  of, 

257 
Parallel  slide  stop  valve,  construction  of, 

256 
Parallel  slide  stop  valve,  operation   of, 

257 

Parsons  dummy  axle  in  turbine,  294 
Parsons  early  duplicate  turbine,  294 
Parsons  turbine,  bearings  of,  295 
Parsons  turbine  blades,  294 
Parsons  turbine,  construction  of,  294 
Parsons  turbine  electric  governor,  297 
Parsons  turbine,  governor  of,  296 
Parsons  turbine  governor,  relay  valve,  297 
Parsons  turbine,  lubrication  in,  296 
Parsons  turbine,  oil  pump  in,  296 
Parsons  turbine  and  ship  propellers,  299 
Parsons  turbo  pump,  298 
Parsons'  vacuum  augmenter,  347 
Peache  engine,  construction  of,  237 
Peache  engine,  course  of  steam  in,  238 
Peache  engine,  governor  of,  239 
Peache  engine,  lubrication  of,  237 
Peache  engine,  valves  of,  237 
Peache  engine,  valve  motion,  range  of,  239 
Pearn's  wall  pump,  173 
Peat,  composition  of,  40 
Peat,  description  of,  40 
Percentage  of  CO.,  in  flue  gas  and  loss  of 

fuel,  207 
Percentage    of    water     vapour    in    air, 

measuring,  28 


4OO 


INDEX 


Period  steam  remains  in  engine,  Willaus 

engine,  234 

Permanent  hardness  in  water,  explana- 
tion of,  180 

Petroleum,  composition  of,  46 
Petroleum,  forms  of,  46 
Petroleum,  groups  of,  47 
Petroleum,  origin  of,  46 
Petroleum,  production  of,  47 
Petroleum  from  shales,  48 
Petroleum,  weight  of,  47 
Pickering  governor,  operation  of,  266 
Pipes  connected  to  injector,  175 
Pipes,  distribution  of  steam  by,  273 
Pipes,  friction  of  steam  in,  heat  generated 

by,  274 

Pipes,  steam,  273 
Pipes,  steam,  arrangement  of,  278 
Pipes,  velocity  of  steam  in,  274 
Piston  drop  valves,  250 
Piston,  power  from,  260 
Piston  rod  and  crank  shaft,  260 
Piston  slide  valve,  248 
Piston  slide  valve,  construction  of,  248 
Piston  slide  valve,  operation  of,  249 
Piston    speed   of    high    and    low-speed 

engines,  228 

Piston  speed  of  engines,  227 
Planimeter  for  indicator  cards,  272 
Plunger  pumps  for  condenser,  363 
Plunger  pumps  with  variable  stroke,  365 
Pochahontas  coals,  41 
Pockets  in  steam  pipes,  278 
Polarization,  4 

Ponds,  cooling,  with  nozzles,  368,  369 
Ponds,  sizes  of,  for  cooling  condensing 

water,  369 

Potential  energy  and  kinetic  energy,  289 
Pounds  and  inches,  vacuum  in,  332 
Power  absorbed  by  condensing  plant,  367 
Power  from  the  piston,  260 
Power  required  to  drive  fan,  147 
Power  required  to  move  air,  147 
Power  required  with  induced  draught, 

142 

Power  taken  from  the  crank  shaft,  261 
Power,  transmitting,  De  Laval  turbine, 

305 

Power  varies  as  cube  of  velocity,  147 
Pressure  of  air   for  boiler  furnace  and 

water  vapour,  28 
Pressure  of  air  creating  draught  in  boiler 

furnace,  28 
Pressure   of   the   atmosphere,  variation 

of,  19 

Pressure  back  in  cylinder,  218 
Pressure  in  boilers,  formula  for,  80 
Pressure   in   centrifugal   fan,   how  pro- 
duced, 146 
Pressure  in  chimney  cooling  tower,  373 


Pressures  in  chimney  with  different  tem- 
peratures outside,  134 
Pressure    of    column    of    hot    gases   in 

chimney,  133 
Pressure  corresponding  to  1-inch  water 

gauge,  129 
Pressure,  effective,  mean  in  steam  engines, 

215 
Pressures,  effective,  with  varying  cut-offs, 

215 
Pressure  of  fan  for  mechanical  draught, 

146 
Pressure  and  impulse  turbines,  difference 

between,  291 

Pressure,  increase  of,  and  boiling  tem- 
perature, 21 

Pressure,  increase  on  surface  of  liquid,  19 
Pressure  injector  can  work  against,  174 
Pressures  required  for  boiler  work,  130 
Pressures  required  for  different  fuels,  130 
Pressures  shown  on  indicator  cards,  272 
Pressure,  steam,  loss  of  in  elbows,  275 
Pressure,  steam,  loss  of  in  valves,  275 
Pressure  steam  turbine,  288 
Pressure  and  superheating,  35 
Pressure  and  temperature,  4 
Pressure  turbine,  action  of  steam  in,  292 
Pressure  turbines,  compounding  in,  292 
Pressure  turbine,  course  of  steam  in,  291 
Pressure  of  vapour  from  surface  of  water, 

19 

Pressure  and  volume,  29 
Pressure  and  volume  of  gas,  formula  for, 

289 

Priming,  and  impurities  in  water,  34 
Prismatic  colours,  2 
Proctor's  mechanical  stoker,  construction 

of,  117 

Producer  gas,  calorific  value  of,  50 
Producer  gas,  composition  of,  50 
Producer  gas,  production  of,  49 
Proell  governor,  construction  of,  266 
Proell  governor,  operation  of,  266 
Prof.  Bateau  and  exhaust  steam  working, 

322 
Prof.  Thurston's  estimate  of  matter  in 

feed  water,  179 
Prof.  Thurston's  standard  for  chimneys, 

132 

Prof.  Tyndal  and  heat  absorption,  11 
Prof.  Weighton,  air  pump  capacity  for 

condenser,  361 
Prof.  Weighton,  condenser  employed  by, 

360 
Prof.  Weighton,  cost  of  circulating  water, 

363 

Prof.  Weighton's  experiments  on   con- 
densers, 360 
Prof.    Weighton,    limit    for    circulating 

water  employed,  363 


INDEX 


401 


Propeller  fan,  construction  of,  145 

Propeller  fan,  use  of,  146 

Protection    of   cooling    towers    without 

vertical  draught,  371 
Pulleys  for  belt  driving,  262 
Pulsometer  feed  pump,  construction  of, 

171 

Pulsometer,  operation  of,  171 
Pumps,  air,  for  condenser,  365 
Pump,  air,  for  jet  condenser,  340 
Pump  for  barometric  condenser,  346 
Pump,  centrifugal,  for  condenser,  363 
Pumps  for  condensers,  363 
Pumps,  Cornish,  driving,  260 
Pumps  for  jet  condenser,  340 
Pumps,  oil,  for  high-speed  engines,  231 
Pumps,  plunger,  with  variable  stroke,  365 
Pumps,  rods  for,  260 
Pumps  for  surface  condenser,  331 
Pump  for  Worthington  jet  condenser,  343 
Pumping  engines,  Cornish,  213 
Punching  boiler  plate,  61 
Pure  anthracite  coals,  composition  of,  41 
Purification    of    water     by    feed-water 

heaters,  167 

Purifying  the  feed  water,  179 
Pyrometer,  expansion,  6 
Pyrometer,  thermo-electric,  7 
Pyrometer,  thermo-electric,  Bristol,  9 
Pyrometer,  thermo-electric,  Crompton,  8 


Q 


Quadruple    expansion  engines,   arrange- 
ment of  cylinders,  227 
Quickly  revolving  engines,  228 


K 


Radial  bricks  for  chimneys,  138 

Radiation  of  heat,  9 

Radiation  from  Lanes,  boilers,  58 

Radiation  from  steam  pipes,  275 

Rainbow,  2 

Rain,  formation  of,  32 

Rams  of  coker  mechanical  stokers,  119 

Ram  pumps,  construction  of,  170 

Ranges  of  valve  motion,  Peache  engine, 

239 

Rateau  methods  of  steam  storage,  324 
Rateau  steam  storage  apparatus,  opera- 
tion of,  325 

Rateau  turbine,  clearance  in,  316 
Rateau  turbine,  construction  of,  315 
Rateau  turbine,  diaphragms  in,  316 
Rateau  turbine,  governor  of,  316 
Rates  of  consumption  with  mechanical 
draught,  133 


Rate    of    combustion   with   mechanical 

stokers,  117 
Rate  of  doing  work,  15 
Rate  of  transmission  of  heat,  formula, 

12 
Reading  steam  engine  indicator  cards, 

272 
Reagents,  importance  of  mixing  in  water 

softening,  182 
Reagents,  measurement  in  Criton  water 

softener,  184 
Reagent,   measurement    of,    in    Reisert 

water  softener,  186 
Reagents  used  in  Criton  water  softener, 

184 

Reaumur  scale,  4 
Receivers   steam,   with  triple-expansion 

engines,  227 
Reciprocating  engine  and  steam  turbine 

compared,  288 

Reciprocating  engines,  vacuum  with,  327 
Reciprocating  steam  engine,  213 
Reciprocating  valves  for  engines,  242 
Recorder,  C(X,  Sarco,  208 
Recorder,  C02,  Simmance,  210 
Reducing  valve,  construction  of,  259 
Reflection,  laws  of,  3 
Refraction,  laws  of,  3 
Refuse  destructor,  colliery,  Meldrum's, 

114 

Refuse  destructor  grate,  Meldrum's,  115 
Refuse,  towns',  burning,  113 
Regulators,  damper,  automatic,  149 
Regulators,  feed  water,  178 
Re-heaters  for  compound  engines,   con- 
struction of,  224 

Re-heating  steam  between  cylinders,  224 
Reid  oil  separator,  operation  of,  197 
Reisert  water  softener,  construction  of, 

186 
Relative  conductive  property  of  thermal 

insulators,  11 
Relay  valve  in  Parsons'  turbine  governor, 

297 

Relief  valve,  atmospheric,  155 
Relief  valves,  steam,  287 
Relief  valves,  Willans  engine,  235 
Removing  oil  from  water,  193 
Removal  of  solid  matter  in  feed-water 

heaters,  167 

Resistance,  thermo  pyrometer,  7 
Reservoir  steam  trap,   construction  of, 

286 

Reservoirs  for  water,  32 
Reversing  engine,  by  eccentrics,  247 
Revolving  wheels  in  Desrumaux  water 

softener,  190 

Riblet  feed-water  heater,  164 
Rings  of  boiler  shells,  arrangement  of, 

62 

2   D 


402 


INDEX 


Ring  system  of  steam  pipes,  279 
Riveting  boiler  shells,  62 
Robb-Mumford    boiler,  construction  of, 

76 

Rocking  fire  bars,  Neil,  108 
Rocking  fire  bar,  Neemes,  110 
Rocking  fire  grate,  Keeler,  109 
Rod  for  pumps,  260 
Ropes,  division  of  load  between,  264 
Rope  drive,  efficiency  of,  265 
Rope  driving  and  crank  shaft,  262 
Rope  drive  and  Lanes,  mill  engines,  240 
Rope  pulleys,  construction  of,  264 
Ropes,  measurement  of,  264 
Rope,  sizes,  formula  for,  265 
Rotary  motion,  production  of,  260 
Row  flexible  water  tube,  166 
Rowland's  mechanical  equivalent  of  heat, 

15 

Royle's  feed-water  heater,  166 
Royle's  evaporators,  205 
Runners  in  Zoelly  turbine,  319 


S 


Safety  and  stop  valve  combined,  156 

Safety  valve,  dead  weight,  154 

Safety  valve,  dead  weight,  Eaves,  155 

Safety  valves,  forms  of,  154 

Safety  valve  lever,  154 

Safety  valve,  low  water,  155 

Safety  valve,  operation  of,  154 

Safety  valves,  reason  for,  152 

Safety  valve  spring,  154 

Salts,  deposit  of,  in  economizer  tubes,  160 

Sarco  automatic  C02  recorder,  208 

Sarco  recorder,  construction  of,  208 

Sarco  recorder,  operation  of,  209 

Saturated  steam,  properties  of,  24,  84 

Saturated  steam,  Siebel,  34 

Saturation  of  air  by  water  vapour,  27 

Sawdust  as  fuel,  46 

Scale  formed  by  impurities  in  water,  33 

Scale  forming  substances  in  boiler  feed, 

181 

Scales  of  temperature,  4 
Schmidt's  separately  fired  superheater, 

202 
Schmidt's  superheater  for  Lanes,  boiler, 

202 

Schultz  boiler,  construction  of,  102 
Schwartzkopff  coal-dust  burning   appa- 
ratus, 111 
Scott  and  Mountain  high-speed  engine, 

construction  of,  232 
Scrapers  for  economizer  tubes,  159 
Scum  cocks  and  foreign  bodies  for  boilers, 

Season,  effect  of,  on  chimney  draught,  135 


Secondary  governor  for  Willans  turbine, 

300 

Sectional  area  of  chimneys,  132 
Semi-anthracite  coals,  composition  of,  41 
Semi-bituminous  coals,  composition  of, 

41 

Semi-bituminous  coals,  properties  of,  42 
Separate  stages  in  Curtis  turbine,  309 
Separators,  oil,  construction  of,  193 
Separator,  oil,  Fletcher,  construction  of, 

194 

Separator,  oil,  Reid,  construction  of,  195 
j   Separator,  steam,  construction  of,  203 
Separator,  steam,  Simms,  204 
Setting  Cornish  boilers,  68 
Setting  Lanes,  boilers,  68 
Settling  tank  in  Criton  water  softener, 

185 
Settling    of    the    wheel    in    De    Laval 

turbine,  303 
Shaft,  crank,  260 
Shales,  description  of,  46 
Shales,  petroleum  from,  48 
Ship  propellers  and  Parsons  turbine,  299 
Shovels  of  coker  mechanical  stokers,  119 
Siebel  and  saturated  steam,  34 
Siebel  and  superheated  steam,  35 
Silicate  cotton,  properties  of,  121 
Simmance  and  Abady  C02  recorder,  210 
Simmance  recorder,  construction  of,  211 
Simmance  recorder,  operation  of,  212 
Simms  feed- water  heater  and  purifier,  169 
Simms  steam  separator,  204 
Simple  engine,  steam,  course  of,  with,  221 
Sinclair  boiler,  course  of  hot  gases,  96 
Sinclair  boiler,  drums  in,  96 
Sinclair  superheater,  203 
Sinclair  water-tube  boiler,  96 
Single  acting  Bumsted  engine,  236 
Single  acting  Willans  engine,  233 
Sirius  steam  trap,  construction  of,  282 
Sirius  steam  trap,  operation  of,  282 
Slide  valves  balanced,  248 
Slide  valve,  description  of,  243 
Slide  valve,  double  ported,  construction 

of,  245 
Slide  valve,  doubled  ported,  operation  of, 

245 

Slide  valve  and  eccentrics,  246 
Slide  valve  and  friction,  248 
Slide  valve,  giving  motion  to,  246 
Slide  valve,  lap  and  lead,  248 
Slide  valve  and  leakage  of  steam,  247 
Slide  valve  and  link  motion,  247 
Slide  valve,  objections  to,  247 
Slide  valve,  operation  of,  245 
Slide  valve,  operation  of,  by  eccentric, 

246 

Slide  valve,  piston,  operation  of,  248,  249 
Slipping  of  belt,  263 


INDEX 


403 


Small  vertical  boilers,  construction  of, 

104 
Smokeless  steam  coals  of  South  Wales, 

41 

SO-j  formation,  heat  liberated,  38 
Solid  condition,  16 
Solid  wooden  cores  in  condenser  tubes, 

360 

Solids,  specific  heats  of,  13 
Solution  of  gas  in  water,  33 
Solution  of  gases  by  water,  32 
Solution  of  rocks  by  water,  32 
Source  of  heat,  best  position  of,  55 
South  Wales  smokeless  steam  coals,  41 
Specific  heat  of  air,  29 
Specific  heat  of  air  with  varying  pressure, 

30 

Specific,  heat  at  constant  pressure,   ex- 
planation of,  30 

Specific   heat   at   constant   volume,   ex- 
planation of,  30 
Specific  heat,  definition  of,  13 
Specific  heats  of  gases,  14,  30 
Specific  heats  of  liquids,  13 
Specific  heats  of  solids,  13 
Specific  heat   of    substances   used  with 

steam,  14 
Specific   heat   of  superheated   steam  at 

atmospheric  pressure,  36 
Specific  heat  and  temperature,  14 
Specific  heat  of  various  substances,  13 
Spectrum,  2 

Speeds  of  De  Laval  turbine,  305 
Speed  of  De  Laval  turbine  wheel,  302 
Speed    of    driving    ropes,    Lanes,    mill 

engine,  241 

Speed  of  Edwards'  air  pump,  367 
Speed  of  highest  efficiency,    De    Laval 

turbine,  302 

"  Speedy  "  type  Thornycroft  boiler,  100 
Spent  tan,  calorific  value  of,  45 
Spiral  baffle  plates  in  Desrumaux  water- 
softener,  190 
Splash  bars,  convex,  for  cooling  towers, 

376 

Splash  lubrication  explained,  228 
Splitting  up  of  furnace  gases  in  multi- 
tubular  boilers,  71 

Spraying  nozzles,  evaporation  from,  370 
Spraying  nozzles,  loss  of  water  with,  370 
Spring  safety  valve,  154 
Sprinkler  mechanical  stoker,  118 
Spur  gearing,  efficiency  of,  265 
Standard  atmospheric  pressure,  18 
Standard  boiling  point  of  water,  19 
Standard  level  for  boiling  point,  18 
Standard  pressure  for  boiling  point,  18 
Steam,  action  of  on  water  in  pockets, 

275 
Steam    --dibiatic  expansion  of,  290 


Steam  boiler,  description  of,  53 
Steam  chest  of  steam  engine,  242 
Steam  consumption  of  condensing  plant, 

Eichard  Allen,  355 
Steam  consumption  with  different  vacua, 

Richard  Allen,  353-354 
Steam,  course  of  with  compound  engine, 

221 
Steam,   course   of    in    enclosed    surface 

condenser,  331 

Steam,   course    of,   in   evaporative  con- 
denser, 334 

Steam,  course  of  in  simple  engine,  221 
Steam,  course    of    in    triple    expansion 

engine,  226 

Steam,  course  of  in  Willans  engine,  233 
Steam  cylinders,  warming,  on  starting 

up,  243 

Steam  distribution,  Willans  engine,  232 
Steam  drums  in  Babcock  boiler,  83 
Steam  drum,  Climax  boiler,  99 
Steam  drum  in  Marshall's  boiler,  91 
Steam  drum,  Nesdrum  boiler,  88 
Steam  and   electrical  distribution  com- 
pared, 273 

Steam  engines,  cut  off  with,  214 
Steam  engines,  early  forms,  214 
Steam  engines,  expansive  working  with, 

214 

Steam  engine,  governor,  use  of,  242 
Steam  engine  indicator,  219 
Steam  engine  indicator,  cards,  271 
Steam  engine  indicator  cards,  reading, 

272 
Steam  engine  indicator,  construction  of, 

270 

Steam  engine  indicator,  Crosby,  270 
Steam  engine  indicator,  operation  of,  271 
Steam  engine,  reciprocating,  213 
Steam  engine,  steam  chest,  242 
Steam  engine,  stop  valve  of,  242 
Steam  engine,  wall,  222 
Steam  engines,  water  hammer  in,  275 
Steam  engine,  work  will  perform,  218 
Steam  engines,  working  pressure  in,  215 
Steam  engines  working  without  expan- 
sion, 214 

Steam  exhaust  head  and  oil  catcher,  197 
Steam,  exhaust,  turbines  working  with, 

322 
Steam,  expansion  of  in  De  Laval  turbine, 

301 

Steam  expansion  for  velocity  turbine,  290 
Steam  feed  pumps,  objection  to,  172 
Steam  feed  pumps,  waste  of  steam  in, 

172 

Steam  feed-water  heaters,  163 
Steam,  flow  of  through  pipes,  table  of, 

276,  277 
Steam  gauge,  construction  of,  152 


404 


INDEX 


Steam     heating    apparatus    in    Arthur 

Koppel  water  softener,  191 
Steam  jacketing  cylinders  for  condensa- 
tion, 217 

Steam  jets,  advantages  claimed  for,  147 
Steam  jets,  arrangement  of,  in  boiler 

furnace,  147 

Steam  jet  and  boiler  tube  cleaning,  151 
Steam  jets,  cooling  of  furnace  bars,  147 
Steam-jet  draught,  adjustable  nozzle  for, 

148 

Steam  jets  and  furnace  draught,  147 
Steam  jets  and  mechanical  stokers,  122 
Steam,  latent  heat  of,  17 
Steam  pipes,  arrangement  of,  278 
Steam  pipes,  drainage  of,  278 
Steam  pipes,  expansion  bends  in,  279 
Steam  pipes,  expansion  and  contraction 

of,  279 
Steam  pipes,  formula  for  loss  of  pressure 

in,  274 

Steam  pipes,  inclination  of,  278 
Steam  pipes,  jointing  of,  278 
Steam  pipes,  jointing  rings  for,  280 
Steam  pipes,  loss  of  heat  by  radiation 

from,  275 

Steam  pipes,  pockets  in,  278 
Steam  pipes,  radiation  from,  275 
Steam  pipes,  ring-main  system  of,  279 
Steam  pipes,  substance,  are  made  of,  273 
Steam  pipes,  support  of,  279 
Steam  pipes,  water  hammer  in,  275 
Steam  pressure,  loss  of  in  elbows,  275 
Steam  pressure,  loss  of  in  valves,  275 
Steam  pressures  used  in  modern  practice, 

36 

Steam  pressures  used  thirty  years  ago,  36 
Steam    pressures,   various,   economy    of 

condensing  with,  367 
Steam    receivers    with    triple-expansion 

engines,  227 

Steam  reheating  between  cylinders,  224 
Steam  relief  valves,  287 
Steam  saturated,  34 
Steam  saturated,  properties  of,  24 
Steam  separator,  construction  of,  203 
Steam  separator,  Marriott,  construction 

of,  203 

Steam  separator,  Simms,  204 
Steam  service,  connection  of  steam  trap 

to,  280 

Steamships,  triple-expansion  engines,  226 
Steam,  sizes  of  pipes  for,  273 
Steam  space  in  Cornish  boilers,  58 
Steam  storage,  Bateau's  methods  of,  324 
Steam,  superheating,  199 
Steam  superheating  for  condensation,  217 
Steam  trap,  Anderson,  operation  of,  286 
Steam  trap,  Brooke,  construction  of,  281 
Steam  traps,  construction  of,  280 


Steam  trap,  Euston,  construction  of,  286 
Steam  trap,  Euston,  operation  of,  286 
Steam  trap,  Lancaster,  construction  of, 

283 

Steam  trap,  Lancaster,  operation  of,  283 
Steam  traps,  lifting  of  water  by,  281 
Steam  trap  Midget,  operation  of,  285 
Steam  traps  operated  by  volatile  spirit, 

285 
Steam  trap    reservoir,    construction   of, 

286 

Steam  trap  reservoir,  operation  of,  286 
Steam  trap,  Sirius,  construction  of,  282 
Steam  trap,  Sirius,  operation  of,  282 
Steam  traps,  use  of,  280 
Steam  trap  water  seal,  construction  of, 

284 

Steam  trap  water  seal,  operation  of,  284 
Steam  turbine  action,  289 
Steam  turbine,  balancing  discs  in,  295 
Steam  turbine,  classes  of,  288 
Steam  turbine,  construction  of,  288 
Steam  turbines,  forms  of  buckets,  322 
Steam  turbines,  forms  of  vanes,  322 
Steam  turbine,   increased   vacuum,    in- 
creased efficiency,  37 
Steam  turbine,  pressure,  288 
Steam  turbine  reaction,  289 
Steam  turbine  and  reciprocating  engine 

compared,  288 
Steam  turbine,  velocity,  288 
Steam  valves  worked  from  crank  shaft, 

262 
Steam,  velocity  of,  in  Worthington  jet 

condenser,  343 
Steam,  volume  of,  34 
Steam  and  water  vapour,  34 
Steel  for  boilers,  testing,  61 
Steel  chimneys,  construction  of,  138 
Steel  chimneys,  supporting,  138 
Steel,  tensile  strength  for  boilers,  61 
Stirling  boiler,  construction  of,  84 
Stirling  boiler,  course  of  hot  gases,  84 
Stirling  boiler,  drums  of,  86 
Stirling  boiler,  feed-water,  86 
Stirling  boiler,  furnace  of,  84 
Stirling  boiler,  mud  drum,  86 
Stirling  boiler,  superheater,  86 
Stirling  superheater,  201 
Stirling  water-tube  boiler,  84 
Stirring  and  water  softeners,  183 
Stoker,  chain  grate,  Babcock,  125 
Stoker  grate  bars,  movement  of,  120 
Stokers  mechanical,  115 
Stokers  mechanical,  chain  grate,  124 
Stokers  mechanical,  overfeed,  117 
Stokers  mechanical,  underfeed,  125 
Stoker  mechanical,  Wilkinson,  122 
Stokers,  overfeed,  grate  bars  of,  120 
Stop  and  safety  valve  combined,  156 


INDEX 


405 


Stop  valves,  angle,  255 

Stop  valve  body,  construction  of,  256 

Stop  valve,   central  pressure,   operation 

of,  259 

Stpp  valves,  construction  of,  242,  254 
Stop    valve,    control    of    steam    supply 

by,  243 

Stop  valves,  globe,  255 
Stop  valves  and  governor,  255 
Stop  valve,  Hopkinson-Ferranti,  257 
Stop  valves,  operation  of,  255 
Stop  valve,  parallel  slide,   construction 

of,  256 

Stop  valve  parallel  slide,  Hopkinson's,  256 
Stop  valve  of  steam  engine,  242 
Stop  valves,  warming,  before  opening,  243 
Storage  of  exhaust  steam  for  turbines,  324 
Storage,  steam,  Rateau's  methods  of,  324 
Strain  on  boiler  shell  with  high  pressures, 

80 

Straker  boiler,  construction  of,  105 
Straker  boiler  and  motor  waggons,  105 
Straker  boiler,  use'of,  105 
Straw,  calorific  value  of,  45 
Specific  heat  of  superheated  steam,  35 
Successive  changes  of  heat,  law  of,  36 
Suckling  boiler,  course  of  hot  gases,  96 
Suckling  boiler,  drums  in,  96 
Suckling  boiler,  water  legs,  96 
Suckling  water-tube  boiler,  96 
Sulphate  of  calcium  in  water,  33 
Sulphate  of  magnesium  in  water,  33 
Sun,  heat  from,  2 
Superheat,  degree  of,  200 
Superheat  required,  quantity,  35 
Superheated  steam  and  lubrication,  231 
Superheated  steam,  Siebel,  35 
Superheated  steam,  specific  heat,  35 
Superheated  steam  and  turbines,  328 
Superheated  steam  in  turbines,  advantage 

of,  328 
Superheated    steam    in    turbines     and 

lubrication,  328 
Superheated  steam,  use  of,  35 
Superheater,  Babcock,  200 
Superheater  in  Babcock  boiler,  83 
Superheaters,  construction  of,  199 
Superheater,  Galloway,  203 
Superheater,  Nesdrum,  202 
Superheater  in  Nesdrum  boiler,  88 
Superheaters,  operation  of,  200 
Superheater,  Schmidt's  for  Lanes,  boiler, 

202 

Superheater  separately  fired  for  Lanca- 
shire boiler,  202 
Superheater,  Sinclair,  203 
Superheater,  Stirling,  201 
Superheater,  Stirling  boiler,  86 
Superheater,    Tinker,    construction     of, 

203 


Superheater,  Tinkers,   fitted  to  Lanca- 
shire boiler,  201 

Superheater,  Woodeson  boiler,  90 
Superheating  in  Atlas  boiler,  94 
Superheating  and  pressure,  35 
Superheating  the  steam,  199 
Superheating  steam    for    condensation, 

217 

Superheating  and  volume,  35 
Superheating  and  watery  vapour,  200 
Supply  of  water  for  injector,  177 
Surface  condenser,  air  effect  in,  332 
Surface  condenser,  air  pump  for,  331 
Surface    condensers    for    the     beds    of 

streams,  338 
Surface    condenser,    circulating    pump 

for,  331 

Surface  condenser,  construction  of,  331 
Surface  condensers,  double  tubes  in,  337 
Surface  condenser,  enclosed,  construction 

of,  331 
Surface  condenser,   enclosed,   course    of 

steam  in,  331 

Surface  condenser,  evaporative,  construc- 
tion of,  344 

Surface  condensers,  open  tank,  338 
Surface  condenser,  pumps  for,  331 
Surface  condensers  versus  jet  condensers, 

341 

Surface  condenser,  Wheeler,  336 
Surface,  cooling  in  condenser  and  I.H.P. 
352 


Table  of  flow  of  steam  through  pipes, 

276,  277 

Table  of  mean  pressures,  216 
Table   of    pressures  for  different  fuels, 

Hutton,  130 
Table  of  working  capacity  of  steam  with 

velocity,  290 

Taking  power  from  the  piston,  260 
Tandem  compound,   horizontal   engine, 

223 
Tandem  compound  condensing    engine 

horizontal,  224 
Taylor  water-tube  boiler,  104 
Temperature  and  pressure,  4 
Temperature  of    the  air  with  Ellis   & 

Eaves  apparatus,  145 
Temperature  at  which  bicarbonates  split 

up,  33 

Temperature  of  cylinder  walls  with  ex- 
pansive working,  217 
Temperatures  of  'combustion  of  towns 

refuse,  114 

Temperature  of  feed  with  injector,  176 
Temperature  of  gases  in  chimney  with 

forced  draught,  140 


406 


INDEX 


Temperature  gradient,  definition  of,  11 
Temperature  of  hot  gases  in  boiler  fur- 
nace, 131 

Temperature  of  hot  gases  in  chimney,  129 
Temperature,  initial,  and  cooling  water 

required,  351 
Temperature  limiting  of    hot  gases  in 

chimney,  129 

Temperatures,  measurement  of,  5 
Temperature  by  melting  points  of  dif- 
ferent substances,  6 
Temperature  of  outside  air  and  chimney 

draught,  134 
Temperature,  scales,  4 
Temperature  and  specific  heat,  14 
Temperature     of     water     delivered     to 

economizer,  161 
Temperature  to  which  feed  water  can  be 

heated  with  exhaust  steam,  166 
Temporary  hardness  in  water,  explana- 
tion of,  180 

Tensile  strength  steel  for  boilers,  61 
Tension  of  water  vapour,  31 
Testing  steel  for  boilers,  61 
Testing  flue  gases  in  chimney,  205 
Tests  of  boiler  furnaces,  65 
Test  of  Curtis  turbo  generator,  313 
Tests  of  De  Laval  turbines  at  different 

loads,  308 

Tests  of  De  Laval  turbine  pumps,  308 
Thermal  storage,  Druitt  Halpin,  327 
Theory  of  heat,  1 

Thermal  conductivity,  definition  of,  11 
Thermal  conductivity  of  finely  divided 

substances,  12 
Thermal  insulators,  11 
Thermal  insulators  and  air  cells,  13 
Thermal  insulator,  dry  air,  12 
Thermo-electric  pyrometer,  7 
Thermometer,  domestic,  5 
Thermometer,  mercurial,  5 
Thermometer,  wet  and  dry  bulb,  use  of, 

28 

Thomson's  calorimeter,  44 
Thornycroft  boiler,  launch  type,  102 
Thornycroft  Marshall  boiler,"  100 
Thornycroft  motor  wagon  boilers,  105 
Thornycroft-Schultz  boiler,  100 
Thornycroft  boiler,  "  Speedy"  type,  100 
Thornycroft  water-tube  boiler,  99 
Three-cylinder  engines  and  cranks,  261 
Throttle  and  expansion  governing,  differ- 
ence between,  268 

Tight  side  and  loose  side  of  belt,  263 
Tinker    superheater,    fitted     to     Lanes. 

boiler,  201 

Tinker  superheater,  construction  of,  203 
Towers,  cooling,  370 
Towers,  cooling,  chimney,  372 
Towers,  cooling,  construction  of,  379 


Towers,  cooling,  without  vertical  draught, 

371 

Towns'  refuse,  burning,  113 
Towns'  refuse,  burning,  draught  with,  114 
Towns'  refuse,  calorific  value  of,  113 
Towns'  refuse  destructors,  construction 

of,  114 

Towns'  refuse,  dust-settling  apparatus,  114 
Transmission  of  heat,  9 
Transmitting  power,  De  Laval  turbine, 

305 

Transporting  water-tube  boilers,  81 
Trap,    steam    connection  of,    to    steam 

service,  280 

Trap,  steam,  Brooke,  construction  of,  281 
Trap,  steam,  water  seal,  construction  of, 

284 

Traps,  steam,  use  of,  280 
Trays  for  water  in  jet  condenser,  341 
i   Treatment  vessels    in    Harris-Anderson 

water  softener,  192 
Tripping  gear  for  drop  valves,  249 
Triple  expansion  engines,  226 
Triple   expansion   engines,  arrangement 

of  cylinders  in,  226 
:  Triple  expansion  condensing  mill  engine, 

horizontal,  240 
j  Triple  expansion  engines,  proportion  of 

cylinders  in,  226 
1   Triple  expansion  engine  receivers,  steam, 

227 

Triple  expansion  engine,  Willans,  234 
Trip  valve,  242 
Tubes,  arrangement  of,  Woodeson  boiler, 

90 
Tubes,  capacity  in  Green's  economizer, 

160 

Tubes  in  Nesdrum  boiler,  87 
Tubes  in  Thornycroft  Marshall  boiler,  100 
Tubes  in  Wheeler  surface  condenser,  337 
Tubes  in  Wood  boiler,  92 
Turbine,  admission  of  steam  to  inter- 
mediate sections,  295 
Turbine,  A.E.G.,  course  of  steam  in,  316 
Turbine  blades,  Parsons,  294 
Turbine  boiler  tube  cleaners,  151 
Turbines  and  condensing,  327 
Turbine,  Curtis,  construction  of,  309 
Turbine,    De    Laval,   highest    efficiency 

speed,  302 

Turbine,  early  duplicate,  Parsons,  294 
Turbine,  end  thrust  in,  294 
Turbine  governor  relay  valve,  Parsons, 

297 

Turbine  governor,  Willans,  300 
Turbine,  Hamilton  Holzwarth,  construc- 
tion of,  321 

Turbines,  intermediate,  289 
Turbine,  length  of,  294 
Turbines,  Parsons,  bearings  of,  295 


INDEX 


407 


Turbine,  Parsons,  construction  of,  292 
Turbines,  pressure  and   impulse,  differ- 
ence between,  291 

Turbines,  pressure,  compounding  in,  292 
Turbine  pumps,  De  Laval,  tests  of,  808 
Turbine,  Bateau,  diapbragms  in,  316 
Turbine,  steam,  balancing  discs  in,  295 
Turbines,  steam,  forms  of  buckets,  382 
Turbines  and  superheated  steam,  328 
Turbines,  vacuum  witb,  332 
Turbine,  Westinghouse,  construction  of, 

313 
Turbine,  Willans  Parsons,  construction 

of,  292 
Turbines  working  with  exhaust  steam, 

322 

Turbine,  Zoelly,  construction  of,  317 
Turbine,  Zoelly,  governor  of,  320 
Turbo  pump,  Parsons,  298 
Turner-Miesse  motor  boiler,  106 
Twin-cylinder  engines,  arrangement  of, 

239 
Two-stage  dry  air  pumps,  365 


U 


Ultimate  analysis  of  fuel,  43 

Ultra  violet  rays,  3 

Underfeed  mechanical  stokers,  125 

Underfeed  mechanical  stoker,  Erith,  126 

Underfeed     Stoker     Co.'s     mechanical 

stoker,  126 

Unit  of  heat  absolute,  14 
Unit  of  mechanical  work  explained,  15 
Use  of  blast  furnace  gas,  50 
Use  of  condenser,  330 
Use  of  cooling  water  for  boiler  feed,  333 
Use  of  the  crank  shaft,  260 
Use  of  hot  gases  to  heat  feed  water,  156 
Use  of  propeller  fan,  145 
Use  of  reducing  valve,  259 
Use  of  steam  traps,  280 
Use  of  stop  valve  in  driving  alternating 

current  generators,  243 
Use  of  Straker  boiler,  105 
Use  of  superheated  steam.  35 
Uses  of  small  vertical  boilers,  104 


Vacua,  different,  cooling  water  required 

with,  Richard  Allen,  356 
Vacua,  high,  and  cooling  water,  351 
Vacuum  augmenter,  advantage  of,  347 
Vacuum    augmenter,    consumption     of 

steam  in,  348 

Vacuum  augmenter,  operation  of,  348 
Vacuum  augmenter,  Parsons,  347 


Vacuum  in  inches  and  pounds,  332 
Vacuum  oil  separator,  Cochrane,  195 
Vacuum  with  reciprocating  engines,  327, 

332 

Vacuum  with  turbines,  327,  332 
Valve,  Corliss,  242 
Valve,  Corliss,  description  of,  251 
Valve,  Corliss,  operation  of,  251 
Valve,  Corliss,  wrist  plate  of,  252 
Valve,  Cornish,  242 
Valves,  Cornish,  description  of,  250 
Valves,  distributing,  of  high-speed  en- 
gines, 231 

Valve,  drop,  242,  249 
Valves,  loss  of  steam  pressure  in,  275 
Valve  motion,  range  of,  Peache  engine, 

239 

Valves,  operation  of,  Peache  engine,  238 
Valves  of  Peache  engine,  237 
Valves,  reciprocating  for  engines,  242 
Valves,  relief,  steam,  287 
Valve,  slide,  242 
Valve,  slide,  piston,  248 
Valve,  stop,  construction  of,  254 
Valve,  stop,  Hopkinson-Ferranti,  257 
Valves,  stop,  operation  of,  255 
Valve,  trip,  242 

Valve,  Wheelock,  construction  of,  253 
Vanes  of  steam  turbines,  forms  of,  322 
Vapour  in  atmosphere  and  barometer 

indications,  19 
Vapour  distribution   chambers  in  Con- 

traflo  condenser,  339 
Vapour  from  surface  of  water,  pressure 

of,  19 

Vapour,  water  and  steam,  34 
Variable-stroke  plunger  pumps,  365 
Variations    of     arrangement    of    tubes, 

water-tube  boilers,  79 
Variation  of  the  boiling-point,  18 
Variation  of  evaporation  with  weather 

369 
Variation  in  pressure  of  the  atmosphere, 

19 

Variation  of  pressure  and  latent  heat,  22 
Variation  of  speed  of  circulating  pump 

for  condenser,  363 

Various  substances,  specific  heats  of,  13 
Velocity     of    circulating     water,     Prof. 

Weighton,  362 
Velocity  of  cooling  water  in  condenser, 

352 
Velocity  of  gases  and  height  of  chimney, 

133 
Velocity  of  steam  impinging  on  De  Laval 

turbine  disc,  302 
Velocity  of  steam,   increase   of,  in  De 

Laval  turbine,  301 
Velocity    of    steam,    increase    of,    with 

lowered  pressure,  291 


408 


INDEX 


Velocity  of  steam  in  pipes,  274 
Velocity  of  steam  in    Worthington  jet 

condenser,  343 
Velocity  steam  turbine,  288 
Velocity  turbine,   steam  expansion  for, 

290 

Ventilation  by  furnace  in  mines,  127 
Vertical  boiler  and    horizontal  engine, 

223 

Vertical  boilers,  small,  104 
Vertical  compound  engines,  arrangement 

of,  239 
Vertical  engine  unenclosed,  compound, 

225 

Vertical  and  horizontal  engines,  239 
Vickers'  mechanical  stoker,  construction 

of,  123 

Vickers  stoker,  feed  of,  124 
Vickers  stoker,  movement  of  fire  bars, 

123 

Vickers  stoker  for  water-tube  boilers,  124 
Volatile  matter  in  coals,  42 
Volatile   spirit,   operating  steam  traps, 

285 
Volume  of  gases  with  induced  draught, 

142 
Volume  of  gases  produced  by  combustion, 

130 

Volume  of  gases  and  width  of  fan,  146 
Volume  and  pressure,  29 
Volume  and  pressure  of  gas,  formula  for, 

289 

Volume  of  steam,  34 
Volume  and  superheating,  35 
Volume  and  weight  of  air  at  various  tem- 
peratures, 26 


W 


Wainwright  corrugated  tube,  166 
Wainwright's  heating  curves  with  plain 

and  corrugated  tubes,  167 
Wall  pumps,  arrangement  of,  173 
Wall  pump,  Pearn,  173 
Wall  steam  engine,  222 
Warming  steam  cylinders  on  starting  up, 

243 

Warming  stop  valves  before  opening,  243 
Waste  of  heat  in  domestic  fire  grate,  54 
Waste  of  heat  in  steam  feed  pumps,  172 
Water-bearing  strata,  32 
Water  below  furnace  in  Lanes,  boilers, 

59 

Water  and  carbonates,  33 
Water  and  chlorides,  33 
Water  circulation,  Climax  boiler,  99 
Water  circulation  in  Nesdrum  boiler,  88 
Water,  composition  of,  31 
Water  for  condensing,  cost  of,  368 


Water  cooling,  333 
Water  cooling,  heat  absorbed  by,  333 
Water  in  Cornish  boilers,  58 
Water,   course  of,  in  evaporative    con- 
denser, 334 

Water,  course  of  water  in  enclosed  sur- 
face condenser,  331 
Water  to  be  employed  for  feed,  179 
Water  employed  for  feed,  course  of,  169 
Water,  evaporation  of,  31 
Water,  evaporation,  cooling  effect  of,  335 
Water,  expansion  of,  16 
Water,  expansion  in  freezing,  16 
Water-  and  fire-tube  boilers,  difference 

between,  77 
Water  and  gases,  course  of  in  economizer, 

160 

Water  in  the  gaseous  state,  31 
Water  gauge,  boiler,  construction  of,  151 
Water  gauge,  construction  of,  129 
Water  gauge,  explanation  of,  129 
Water  gauge  1-inch  pressure,  correspond- 
ing to,  129 

Water  hammer  in  steam  engines,  275 
Water  hammer  in  steam  pipes,  275 
Water  jet  in  Worthington  jet  condenser, 

342 

Water  in  Lanes,  boilers,  58 
Water,  latent  heat  of,  17 
Water  legs  in  Marshall's  boiler,  91 
Water  legs  in  Suckling  boiler,  96 
Water  in  the  liquid  state,  31 
Water  lost  by  evaporation,  335 
Water,  oil,  removing  from,  193 
Water  in  pockets,  action  of  steam  on,  278 
Water     purifying    apparatus    of    Atlas 

boiler,  95 

Water  and  reagents,  course  of  in  Harris- 
Anderson  apparatus,  193 
Water  safety  apparatus,  155 
Water  seal  steam  trap,  construction  of, 

284 

Water  seal  steam  trap,  operation  of,  284 
Water  softener,  Archbutt-  Deely,  183 
Water   softener,   Bruun  -  Lowener,  con- 
struction of,  187 

Water  softeners,  construction  of,  182 
Water  softener,  Criton,  construction  of, 

184 
Water  softener,  Desrumaux,  construction 

of,  190 
Water  softener,  Doulton,  construction  of, 

188 

Water  softeners  and  filters,  183 
Water  softener,  Guttmann,  construction 

of,  188 

Water  softener,  Harris-Amderson,   con- 
struction of,  192 

Water  softeners,  importance  of  mixing 
reagents,  182 


INDEX 


409 


Water  softener,  Kennicott,  construction 

of,  189 

Water    softener,    Arthur    Koppel,    con- 
struction of,  191 
Water  softener  for  locomotive   boilers, 

Keisert,  187 
Water  softener,  Beisert,  construction  of, 

186 

Water  softeners  and  stirring,  183 
Water  softening  and  analysis,  182 
Water  in  the  solid  state,  31 
Water  and  sulphates,  33 
Water  surface  in  Cornish  boiler,  60 
Water  surface  in  Lanes,  boiler,  60 
Water  tanks  on  chimneys,  138 
Water,    temperature     of,    delivered     to 

economizer,  161 

Water  trays  in  jet  condenser.  341 
Water  tubes  of  Climax  boiler,  98 
Water-tube  boilers,  advantage  with  high 

pressures,  79 

Water-tube  boilers,  ashpits  in,  82,  107 
Water-tube  boiler,  Atlas,  93 
Water-tube  boiler,  Babcock,  82 
Water-tube  boilers,  brickwork,  78 
Water-tube  boilers,  circulation,  81 
Water-tube  boiler,  Climax,  98 
Water-tube  boilers,  construction  of,  77 
Water-tube  boiler,  Davey-Paxman,  con- 
struction of,  91 
Water-tube  boiler,  Detroit,  95 
Water-tube  boilers,  fire  bars,  82 
Water-tube  boilers,  furnace  of,  82 
Water-tube  boilers,  furnace  grates,  107 
Water-tube  boiler,  Galloway,  93 
Water-tube  boiler,  Heine,  95 
Water-tube  boilers  with  horizontal  tubes, 

90 

Water-tube  boilers,  iron  work  for,  78 
Water-tube  boilers,  largest  diameters  of 

vessels  in,  81 

Water-tube  boiler,  Marshall,  91 
Water-tube  boiler,  Nesdrum,  87 
Water-tube  boiler,  Sinclair,  96 
Water-tube  boiler,  Stirling,  84 
Water-tube  boiler,  Suckling,  construction 

of,  96 

Water-tube  boiler,  Taylor,  104 
Water-tube  boiler,  Thornycroft,  99 
Water-tube  boilers,  transporting,  81 
Water-tube  boilers,  various  arrangements 

of  tubes,  79 

Water-tube  boilers,  Vickers  stoker,  124 
Water-tube  boiler,  Wood,  92 
Water-tube  boiler,  Woodeson,  88 
Water-tube  boilers,  working  of,  79 
Water  vapour  and  air,  25 
Water  vapour  in  air  and  blast  furnaces,  27 
Water  vapour  in  air  in  different  months, 
27 


Water  vapour  in  atmosphere,  18 
Water  vapour,  condensation  of,  34 
Water  vapour  and  cylinder  condensation, 

217 

Water  vapour,  elastic  force  of,  27 
Water  vapour  and  expansive  working, 

217 

Water  vapour  and  steam,  34 
Water  vapour,  tension  of,  31 
Water  from  wells,  32 
Water,  where  it  comes  from,  31 
Watery  vapour  and  superheating,  200 
Wave  theory  of  heat,  1 
Waves,  characteristics  of,  1 
Weight  of  air,  18 
Weight  of  column  of  air  above  the  earth, 

18 

Weight  of  petroleum,  47 
Weight  and   volume  of  air  at  various 

temperatures,  26 

Weighton,   Prof.,   experiments    on   con- 
densers, 360 
Weir's  evaporators,  205 
Wells  for  water,  32 
Westinghouse   turbine,  construction  of, 

313 
Westinghouse  turbine,  course  of   steam 

in,  315 
Westinghouse  turbine   on   Metropolitan 

District  Railway,  313 
Wet  back  boiler,  74 

Wet  and  dry  bulb  thermometer,  use  of,  28 
Wheeler  combined  condenser  and  pump 

plant,  337 

Wheeler  surface  condenser,  tubes  in,  337 
Wheelock     expansion     gear     for     mill 

engines,  241 

Wheelock  valve,  construction  of,  253 
Wheelock  valve,  description  of,  242 
White  boiler,  construction  of,  106 
White  light,  composition  of,  2 
White  motor- waggon  boiler,  106 
Width  of  fan  for  mechanical  draught,  146 
Wilkinson  mechanical  stoker,  122 
Willans  central  valve  engine,  232 
Willans  engine,  air  cylinder,  233 
Willans  engine,  arrangement  of  cranks, 

233 
Willans  engine,  arrangement  of  cylinders 

in,  232 
Willans  engine,  arrangement  of  cylinders, 

compound,  234 
Willans  engine,  brasses  in  compression, 

233 
Willans  engine,  compressed  air,  heat  in, 

234 

Willans  engine,  course  of  steam,  233 
Willans  engine,  distributing  valve,  232 
Willans  engine,  governor  of,  235 
Willans  engine  relief  valves,  235 


INDEX 


Willans  engine,  single  acting,  233 

Wilians  engine,  steam  distribution,  232 

Willans  engine,  work  in  compressing  air, 
234 

Willans-Parsons  turbine,  construction  of, 
292 

Willans  triple-expansion  engine,  arrange- 
ment of,  234 

Willans  turbine  blades,  construction  of, 
293 

Willans  turbine  governor,  300 

Willans  turbine,  lubrication  of,  300 

Willans  turbine,  secondary  governor,  300 

Williams  feed-water  regulator,  construc- 
tion of,  179 

Wilson  Hartnell's  expansion  governor, 
267 

Wires  used  in  thermo-electric  pyrometer, 
7 

Wood  boiler,  construction  of,  92 

Wood  boiler,  course  of  hot  gases  in,  93 

Wood  boilers,  headers  in,  92 

Wood  boiler,  tubes  in,  92 

Wood,  calorific  value  of,  45 

Wood,  composition  of,  44 

Wood  for  cooling  towers,  379 

Wood,  measurement  of,  45 

Wood  water-tube  boiler,  92 

Wood  wool  filter  in  Bruun  Lowener 
water  softener,  188 

Wooden  cores  in  condenser  tubes,  360 

Wooden  gratings  in  cooling  towers,  377 

Woodeson  boiler,  arrangement  of  tubes. 
90 


Woodeson  boiler,  construction  of,  88 
Woodeson  boiler,  furnace  of,  88 
Woodeson  boiler,  mud  drums,  90 
Woodeson  boiler,  superheater,  90 
Woodeson  water-tube  boiler,  88 
Work  in  compressing  air,  Willans  engine, 

234 

Work  steam  engine  will  perform,  218 
Working  pressure  in  steam  engines,  215 
Working  of  water-tube  boilers,  79 
Worm  gearing,  arrangement  of,  265 
Worm  gearing,  efficiency  of,  265 
Worthington  boiler  feed  pump,  construc- 
tion of,  171 

Worthington  Co.'s  cooling  tower,  377 
Worthington  jet  condenser,  water  jet  in, 

342 

Wrist  plate  of  Corliss  valve,  252 
Weinland  boiler  tube  cleaner,  150 
Weinland  turbine  boiler  tube  cleaner,  151 


Z 


Zoelly  turbine,  bearings  in,  319 
Zoelly  turbine,  clearance  in,  319 
Zoelly  turbine,  construction  of,  317 
Zoelly  turbine,  emergency  governor  in, 

320 

Zoelly  turbine  and  exhaust  steam,  329 
Zoelly  turbine,  governor  of,  320 
Zoelly  turbine  governor,  oil  relay  in,  320 
Zoelly  turbine,  overload  valve  in,  321 
Zoelly  turbine,  runners  in,  319 


Kii 


THE   END 


PfilNTED    BT   WILLIAM   CLOWES   AND  SONS,   LIMITED,   LONDON   AND  BKCCLES. 


BOOK 


OVERDUE.  $K°°    °"    THE 


181025 


XI 


